[PATCH v4 0/2] Support dates outside of 1901..2038 range

[PATCH v4 0/2] Support dates outside of 1901..2038 range

[Andrew Hamilton]

Support dates outside of 1901..2038.
Add tests for dates outside this range.
Vast majority of the work was done by Vladimir Serbinenko

Fixes: https://savannah.gnu.org/bugs/?63894
Fixes: https://savannah.gnu.org/bugs/?66301

V3 -> V4: Add additional commentary for a few magic numbers
 and fix some coding standard issues.

V2 -> V3: Added additional commentary to datetime.c to describe
 the origin of some of the numbers used in calculations.

Andrew Hamilton (2):
  datetime: Support dates outside of 1901..2038 range
  date_unit_test: test dates outside of 32-bit unix range

 grub-core/lib/datetime.c | 64 ++++++++++++++++++++++++++++++++--------
 include/grub/datetime.h  | 27 ++++++++++++-----
 tests/date_unit_test.c   | 44 +++++++++++++++++++++------
 3 files changed, 106 insertions(+), 29 deletions(-)

-- 
2.39.5


_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

[PATCH v4 1/2] datetime: Support dates outside of 1901..2038 range

[Andrew Hamilton]

Support dates outside of 1901..2038.

Fixes: https://savannah.gnu.org/bugs/?63894
Fixes: https://savannah.gnu.org/bugs/?66301

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
---
 grub-core/lib/datetime.c | 64 ++++++++++++++++++++++++++++++++--------
 include/grub/datetime.h  | 27 ++++++++++++-----
 2 files changed, 71 insertions(+), 20 deletions(-)

diff --git a/grub-core/lib/datetime.c b/grub-core/lib/datetime.c
index 8f0922fb0..a0f84d989 100644
--- a/grub-core/lib/datetime.c
+++ b/grub-core/lib/datetime.c
@@ -64,7 +64,10 @@ grub_get_weekday_name (struct grub_datetime *datetime)
 #define SECPERDAY (24*SECPERHOUR)
 #define DAYSPERYEAR 365
 #define DAYSPER4YEARS (4*DAYSPERYEAR+1)
-
+/* 24 leap years in 100 years */
+#define DAYSPER100YEARS (100 * DAYSPERYEAR + 24)
+/* 97 leap years in 400 years */
+#define DAYSPER400YEARS (400 * DAYSPERYEAR + 97)
 
 void
 grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
@@ -76,10 +79,12 @@ grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
   /* Convenience: let's have 3 consecutive non-bissextile years
      at the beginning of the counting date. So count from 1901. */
   int days_epoch;
-  /* Number of days since 1st Januar, 1901.  */
+  /* Number of days since 1st January, 1 (proleptic). */
   unsigned days;
   /* Seconds into current day.  */
   unsigned secs_in_day;
+  /* Tracks whether this is a leap year. */
+  bool is_bisextile;
 
   /* Transform C divisions and modulos to mathematical ones */
   if (nix < 0)
@@ -92,27 +97,62 @@ grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
     days_epoch = grub_divmod64 (nix, SECPERDAY, NULL);
 
   secs_in_day = nix - days_epoch * SECPERDAY;
-  days = days_epoch + 69 * DAYSPERYEAR + 17;
+  /*
+   * 1970 is Unix Epoch. Adjust to a year 1 epoch:
+   *  Leap year logic:
+   *   - Years evenly divisible by 400 are leap years
+   *   - Otherwise, if divisible by 100 are not leap years
+   *   - Otherwise, if divisible by 4 are leap years
+   *  There are four 400-year periods (1600 years worth of days with leap days)
+   *  There are three 100-year periods worth of leap days (3*24)
+   *  There are 369 years in addition to the four 400 year periods
+   *  There are 17 leap days in 69 years (beyond the three 100 year periods)
+   */
+  days = days_epoch + 369 * DAYSPERYEAR + 17 + 24 * 3 + 4 * DAYSPER400YEARS;
+
+  datetime->year = 1 + 400 * (days / DAYSPER400YEARS);
+  days %= DAYSPER400YEARS;
 
-  datetime->year = 1901 + 4 * (days / DAYSPER4YEARS);
+  /*
+   * On 31st December of bissextile (leap) years 365 days from the beginning
+   * of the year elapsed but year isn't finished yet - every 400 years
+   * 396 is 4 years less than 400 year leap cycle
+   * 96 is 1 day less than number of leap days in 400 years
+   */
+  if (days / DAYSPER100YEARS == 4)
+    {
+      datetime->year += 396;
+      days -= 396 * DAYSPERYEAR + 96;
+    }
+  else
+    {
+      datetime->year += 100 * (days / DAYSPER100YEARS);
+      days %= DAYSPER100YEARS;
+    }
+
+  datetime->year += 4 * (days / DAYSPER4YEARS);
   days %= DAYSPER4YEARS;
-  /* On 31st December of bissextile years 365 days from the beginning
-     of the year elapsed but year isn't finished yet */
+  /*
+   * On 31st December of bissextile (leap) years 365 days from the beginning
+   * of the year elapsed but year isn't finished yet - every 4 years
+   */
   if (days / DAYSPERYEAR == 4)
     {
       datetime->year += 3;
-      days -= 3*DAYSPERYEAR;
+      days -= 3 * DAYSPERYEAR;
     }
   else
     {
       datetime->year += days / DAYSPERYEAR;
       days %= DAYSPERYEAR;
     }
-  for (i = 0; i < 12
-	 && days >= (i==1 && datetime->year % 4 == 0
-		      ? 29 : months[i]); i++)
-    days -= (i==1 && datetime->year % 4 == 0
-			    ? 29 : months[i]);
+
+  is_bisextile = datetime->year % 4 == 0
+                 && (datetime->year % 100 != 0 || datetime->year % 400 == 0);
+  for (i = 0;
+       i < 12 && days >= ((i == 1 && is_bisextile == true) ? 29 : months[i]);
+       i++)
+    days -= ((i == 1 && is_bisextile == true) ? 29 : months[i]);
   datetime->month = i + 1;
   datetime->day = 1 + days;
   datetime->hour = (secs_in_day / SECPERHOUR);
diff --git a/include/grub/datetime.h b/include/grub/datetime.h
index bcec636f0..ff847e847 100644
--- a/include/grub/datetime.h
+++ b/include/grub/datetime.h
@@ -54,8 +54,9 @@ void grub_unixtime2datetime (grub_int64_t nix,
 static inline int
 grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
 {
-  grub_int32_t ret;
+  grub_int64_t ret;
   int y4, ay;
+  bool is_bisextile;
   const grub_uint16_t monthssum[12]
     = { 0,
 	31,
@@ -75,15 +76,11 @@ grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
   const int SECPERHOUR = 60 * SECPERMIN;
   const int SECPERDAY = 24 * SECPERHOUR;
   const int SECPERYEAR = 365 * SECPERDAY;
-  const int SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
+  const grub_int64_t SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
 
-  if (datetime->year > 2038 || datetime->year < 1901)
-    return 0;
   if (datetime->month > 12 || datetime->month < 1)
     return 0;
 
-  /* In the period of validity of unixtime all years divisible by 4
-     are bissextile*/
   /* Convenience: let's have 3 consecutive non-bissextile years
      at the beginning of the epoch. So count from 1973 instead of 1970 */
   ret = 3 * SECPERYEAR + SECPERDAY;
@@ -94,13 +91,27 @@ grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
   ret += y4 * SECPER4YEARS;
   ret += ay * SECPERYEAR;
 
+  /*
+   * Correct above calculation (which assumes every 4 years is a leap year)
+   * to remove those "false leap years" that are divisible by 100 but not 400.
+   * Since this logic starts with seconds since 1973, 15 is used because:
+   *  - (1973 - 1) / 100 = 19 (floor due to integer math)
+   *  - (1973 - 1) / 400 = 4 (floor due to integer math)
+   *  - 19 - 4 - 15 = 0 (we want to start with no "false leap years" at time
+   *     zero of 1973)
+   */
+  ret -= ((datetime->year - 1) / 100 - (datetime->year - 1) / 400 - 15)
+         * SECPERDAY;
+
   ret += monthssum[datetime->month - 1] * SECPERDAY;
-  if (ay == 3 && datetime->month >= 3)
+  is_bisextile = ay == 3
+                 && (datetime->year % 100 != 0 || datetime->year % 400 == 0);
+  if (is_bisextile && datetime->month >= 3)
     ret += SECPERDAY;
 
   ret += (datetime->day - 1) * SECPERDAY;
   if ((datetime->day > months[datetime->month - 1]
-       && (!ay || datetime->month != 2 || datetime->day != 29))
+       && !(is_bisextile && datetime->month == 2 && datetime->day == 29))
       || datetime->day < 1)
     return 0;
 
-- 
2.39.5


_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

[PATCH v4 2/2] date_unit_test: test dates outside of 32-bit unix range

[Andrew Hamilton]

Add tests outside the date range possible with 32-bit time
calculation.

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
---
 tests/date_unit_test.c | 44 +++++++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/tests/date_unit_test.c b/tests/date_unit_test.c
index 99774f199..aec3dc3e4 100644
--- a/tests/date_unit_test.c
+++ b/tests/date_unit_test.c
@@ -25,12 +25,13 @@
 #include <grub/test.h>
 
 static void
-date_test (grub_int32_t v)
+date_test (grub_int64_t v)
 {
   struct grub_datetime dt;
   time_t t = v;
   struct tm *g;
   int w;
+  grub_int64_t back = 0;
 
   g = gmtime (&t);
 
@@ -38,28 +39,41 @@ date_test (grub_int32_t v)
 
   w = grub_get_weekday (&dt);
 
-  grub_test_assert (g->tm_sec == dt.second, "time %d bad second: %d vs %d", v,
+  grub_datetime2unixtime (&dt, &back);
+
+  grub_test_assert (g->tm_sec == dt.second, "time %lld bad second: %d vs %d", (long long) v,
 		    g->tm_sec, dt.second);
-  grub_test_assert (g->tm_min == dt.minute, "time %d bad minute: %d vs %d", v,
+  grub_test_assert (g->tm_min == dt.minute, "time %lld bad minute: %d vs %d", (long long) v,
 		    g->tm_min, dt.minute);
-  grub_test_assert (g->tm_hour == dt.hour, "time %d bad hour: %d vs %d", v,
+  grub_test_assert (g->tm_hour == dt.hour, "time %lld bad hour: %d vs %d", (long long) v,
 		    g->tm_hour, dt.hour);
-  grub_test_assert (g->tm_mday == dt.day, "time %d bad day: %d vs %d", v,
+  grub_test_assert (g->tm_mday == dt.day, "time %lld bad day: %d vs %d", (long long) v,
 		    g->tm_mday, dt.day);
-  grub_test_assert (g->tm_mon + 1 == dt.month, "time %d bad month: %d vs %d", v,
+  grub_test_assert (g->tm_mon + 1 == dt.month, "time %lld bad month: %d vs %d",(long long) v,
 		    g->tm_mon + 1, dt.month);
   grub_test_assert (g->tm_year + 1900 == dt.year,
-		    "time %d bad year: %d vs %d", v,
+                   "time %lld bad year: %d vs %d", (long long) v,
 		    g->tm_year + 1900, dt.year);
-  grub_test_assert (g->tm_wday == w, "time %d bad week day: %d vs %d", v,
+  grub_test_assert (g->tm_wday == w, "time %lld bad week day: %d vs %d", (long long) v,
 		    g->tm_wday, w);
+  grub_test_assert (back == v, "time %lld bad back transform: %lld", (long long) v,
+                   (long long) back);
 }
 
 static void
 date_test_iter (void)
 {
-  grub_int32_t tests[] = { -1, 0, +1, -2133156255, GRUB_INT32_MIN,
+  grub_int32_t tests[] = { -1, 0, +1, 978224552, -2133156255, -2110094321, GRUB_INT32_MIN,
 			   GRUB_INT32_MAX };
+  /*
+   * Test several known UNIX timestamps outside 32-bit time:
+   *   1. 5774965200:  2152-12-31 21:00:00  - Leap year
+   *   2. 4108700725:  2100-03-14 09:45:25  - Not a leap year
+   *   3. -5029179792: 1810-08-19 21:36:48  - Not a leap year
+   */
+  grub_int64_t tests64[] = { (grub_int64_t) 5774965200,
+                             (grub_int64_t) 4108700725,
+                             (grub_int64_t) -5029179792 };
   unsigned i;
 
   for (i = 0; i < ARRAY_SIZE (tests); i++)
@@ -71,6 +85,18 @@ date_test_iter (void)
       date_test (x);
       date_test (-x);
     }
+
+  if (sizeof (time_t) > 4)
+    {
+      for (i = 0; i < ARRAY_SIZE (tests64); i++)
+        date_test (tests64[i]);
+      for (i = 0; i < 10000000; i++)
+        {
+          /* Ranges from 0064 to 6869. */
+          grub_int64_t x = rand () + (rand () % 100 - 28) * (grub_uint64_t) GRUB_INT32_MAX;
+          date_test (x);
+        }
+    }
 }
 
 GRUB_UNIT_TEST ("date_unit_test", date_test_iter);
-- 
2.39.5


_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

Re: [PATCH v4 1/2] datetime: Support dates outside of 1901..2038 range

[Daniel Kiper via Grub-devel]

On Mon, Aug 25, 2025 at 10:17:37PM -0500, Andrew Hamilton wrote:
> Support dates outside of 1901..2038.
>
> Fixes: https://savannah.gnu.org/bugs/?63894
> Fixes: https://savannah.gnu.org/bugs/?66301
>
> Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
> Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
> ---
>  grub-core/lib/datetime.c | 64 ++++++++++++++++++++++++++++++++--------
>  include/grub/datetime.h  | 27 ++++++++++++-----
>  2 files changed, 71 insertions(+), 20 deletions(-)
>
> diff --git a/grub-core/lib/datetime.c b/grub-core/lib/datetime.c
> index 8f0922fb0..a0f84d989 100644
> --- a/grub-core/lib/datetime.c
> +++ b/grub-core/lib/datetime.c
> @@ -64,7 +64,10 @@ grub_get_weekday_name (struct grub_datetime *datetime)
>  #define SECPERDAY (24*SECPERHOUR)
>  #define DAYSPERYEAR 365
>  #define DAYSPER4YEARS (4*DAYSPERYEAR+1)
> -
> +/* 24 leap years in 100 years */
> +#define DAYSPER100YEARS (100 * DAYSPERYEAR + 24)
> +/* 97 leap years in 400 years */
> +#define DAYSPER400YEARS (400 * DAYSPERYEAR + 97)
>
>  void
>  grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
> @@ -76,10 +79,12 @@ grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
>    /* Convenience: let's have 3 consecutive non-bissextile years
>       at the beginning of the counting date. So count from 1901. */
>    int days_epoch;
> -  /* Number of days since 1st Januar, 1901.  */
> +  /* Number of days since 1st January, 1 (proleptic). */
>    unsigned days;
>    /* Seconds into current day.  */
>    unsigned secs_in_day;
> +  /* Tracks whether this is a leap year. */
> +  bool is_bisextile;
>
>    /* Transform C divisions and modulos to mathematical ones */
>    if (nix < 0)
> @@ -92,27 +97,62 @@ grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime *datetime)
>      days_epoch = grub_divmod64 (nix, SECPERDAY, NULL);
>
>    secs_in_day = nix - days_epoch * SECPERDAY;
> -  days = days_epoch + 69 * DAYSPERYEAR + 17;
> +  /*
> +   * 1970 is Unix Epoch. Adjust to a year 1 epoch:
> +   *  Leap year logic:
> +   *   - Years evenly divisible by 400 are leap years
> +   *   - Otherwise, if divisible by 100 are not leap years
> +   *   - Otherwise, if divisible by 4 are leap years
> +   *  There are four 400-year periods (1600 years worth of days with leap days)
> +   *  There are three 100-year periods worth of leap days (3*24)
> +   *  There are 369 years in addition to the four 400 year periods
> +   *  There are 17 leap days in 69 years (beyond the three 100 year periods)
> +   */
> +  days = days_epoch + 369 * DAYSPERYEAR + 17 + 24 * 3 + 4 * DAYSPER400YEARS;
> +
> +  datetime->year = 1 + 400 * (days / DAYSPER400YEARS);
> +  days %= DAYSPER400YEARS;
>
> -  datetime->year = 1901 + 4 * (days / DAYSPER4YEARS);
> +  /*
> +   * On 31st December of bissextile (leap) years 365 days from the beginning
> +   * of the year elapsed but year isn't finished yet - every 400 years
> +   * 396 is 4 years less than 400 year leap cycle
> +   * 96 is 1 day less than number of leap days in 400 years
> +   */
> +  if (days / DAYSPER100YEARS == 4)
> +    {
> +      datetime->year += 396;
> +      days -= 396 * DAYSPERYEAR + 96;
> +    }
> +  else
> +    {
> +      datetime->year += 100 * (days / DAYSPER100YEARS);
> +      days %= DAYSPER100YEARS;
> +    }
> +
> +  datetime->year += 4 * (days / DAYSPER4YEARS);
>    days %= DAYSPER4YEARS;
> -  /* On 31st December of bissextile years 365 days from the beginning
> -     of the year elapsed but year isn't finished yet */
> +  /*
> +   * On 31st December of bissextile (leap) years 365 days from the beginning
> +   * of the year elapsed but year isn't finished yet - every 4 years
> +   */
>    if (days / DAYSPERYEAR == 4)
>      {
>        datetime->year += 3;
> -      days -= 3*DAYSPERYEAR;
> +      days -= 3 * DAYSPERYEAR;
>      }
>    else
>      {
>        datetime->year += days / DAYSPERYEAR;
>        days %= DAYSPERYEAR;
>      }
> -  for (i = 0; i < 12
> -	 && days >= (i==1 && datetime->year % 4 == 0
> -		      ? 29 : months[i]); i++)
> -    days -= (i==1 && datetime->year % 4 == 0
> -			    ? 29 : months[i]);
> +
> +  is_bisextile = datetime->year % 4 == 0
> +                 && (datetime->year % 100 != 0 || datetime->year % 400 == 0);

Even if it works it is not fully correct...

is_bisextile = (datetime->year % 4 == 0 &&
                (datetime->year % 100 != 0 || datetime->year % 400 == 0)) ? true : false;

> +  for (i = 0;
> +       i < 12 && days >= ((i == 1 && is_bisextile == true) ? 29 : months[i]);
> +       i++)
> +    days -= ((i == 1 && is_bisextile == true) ? 29 : months[i]);
>    datetime->month = i + 1;
>    datetime->day = 1 + days;
>    datetime->hour = (secs_in_day / SECPERHOUR);
> diff --git a/include/grub/datetime.h b/include/grub/datetime.h
> index bcec636f0..ff847e847 100644
> --- a/include/grub/datetime.h
> +++ b/include/grub/datetime.h
> @@ -54,8 +54,9 @@ void grub_unixtime2datetime (grub_int64_t nix,
>  static inline int
>  grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
>  {
> -  grub_int32_t ret;
> +  grub_int64_t ret;
>    int y4, ay;
> +  bool is_bisextile;
>    const grub_uint16_t monthssum[12]
>      = { 0,
>  	31,
> @@ -75,15 +76,11 @@ grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
>    const int SECPERHOUR = 60 * SECPERMIN;
>    const int SECPERDAY = 24 * SECPERHOUR;
>    const int SECPERYEAR = 365 * SECPERDAY;
> -  const int SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
> +  const grub_int64_t SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
>
> -  if (datetime->year > 2038 || datetime->year < 1901)
> -    return 0;
>    if (datetime->month > 12 || datetime->month < 1)
>      return 0;
>
> -  /* In the period of validity of unixtime all years divisible by 4
> -     are bissextile*/
>    /* Convenience: let's have 3 consecutive non-bissextile years
>       at the beginning of the epoch. So count from 1973 instead of 1970 */
>    ret = 3 * SECPERYEAR + SECPERDAY;
> @@ -94,13 +91,27 @@ grub_datetime2unixtime (const struct grub_datetime *datetime, grub_int64_t *nix)
>    ret += y4 * SECPER4YEARS;
>    ret += ay * SECPERYEAR;
>
> +  /*
> +   * Correct above calculation (which assumes every 4 years is a leap year)
> +   * to remove those "false leap years" that are divisible by 100 but not 400.
> +   * Since this logic starts with seconds since 1973, 15 is used because:
> +   *  - (1973 - 1) / 100 = 19 (floor due to integer math)
> +   *  - (1973 - 1) / 400 = 4 (floor due to integer math)
> +   *  - 19 - 4 - 15 = 0 (we want to start with no "false leap years" at time
> +   *     zero of 1973)
> +   */
> +  ret -= ((datetime->year - 1) / 100 - (datetime->year - 1) / 400 - 15)
> +         * SECPERDAY;
> +
>    ret += monthssum[datetime->month - 1] * SECPERDAY;
> -  if (ay == 3 && datetime->month >= 3)
> +  is_bisextile = ay == 3
> +                 && (datetime->year % 100 != 0 || datetime->year % 400 == 0);

Again...

is_bisextile = (ay == 3 && (datetime->year % 100 != 0 || datetime->year % 400 == 0)) ? true : false;

> +  if (is_bisextile && datetime->month >= 3)

is_bisextile == true && ...

>      ret += SECPERDAY;
>
>    ret += (datetime->day - 1) * SECPERDAY;
>    if ((datetime->day > months[datetime->month - 1]
> -       && (!ay || datetime->month != 2 || datetime->day != 29))
> +       && !(is_bisextile && datetime->month == 2 && datetime->day == 29))

is_bisextile == true && ...

... and I would drop "is_" from variable name...

Daniel

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

Re: [PATCH v4 2/2] date_unit_test: test dates outside of 32-bit unix range

[Daniel Kiper via Grub-devel]

On Mon, Aug 25, 2025 at 10:17:38PM -0500, Andrew Hamilton wrote:
> Add tests outside the date range possible with 32-bit time
> calculation.
>
> Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
> Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
> ---
>  tests/date_unit_test.c | 44 +++++++++++++++++++++++++++++++++---------
>  1 file changed, 35 insertions(+), 9 deletions(-)
>
> diff --git a/tests/date_unit_test.c b/tests/date_unit_test.c
> index 99774f199..aec3dc3e4 100644
> --- a/tests/date_unit_test.c
> +++ b/tests/date_unit_test.c
> @@ -25,12 +25,13 @@
>  #include <grub/test.h>
>
>  static void
> -date_test (grub_int32_t v)
> +date_test (grub_int64_t v)
>  {
>    struct grub_datetime dt;
>    time_t t = v;
>    struct tm *g;
>    int w;
> +  grub_int64_t back = 0;
>
>    g = gmtime (&t);
>
> @@ -38,28 +39,41 @@ date_test (grub_int32_t v)
>
>    w = grub_get_weekday (&dt);
>
> -  grub_test_assert (g->tm_sec == dt.second, "time %d bad second: %d vs %d", v,
> +  grub_datetime2unixtime (&dt, &back);
> +
> +  grub_test_assert (g->tm_sec == dt.second, "time %lld bad second: %d vs %d", (long long) v,
>  		    g->tm_sec, dt.second);
> -  grub_test_assert (g->tm_min == dt.minute, "time %d bad minute: %d vs %d", v,
> +  grub_test_assert (g->tm_min == dt.minute, "time %lld bad minute: %d vs %d", (long long) v,
>  		    g->tm_min, dt.minute);
> -  grub_test_assert (g->tm_hour == dt.hour, "time %d bad hour: %d vs %d", v,
> +  grub_test_assert (g->tm_hour == dt.hour, "time %lld bad hour: %d vs %d", (long long) v,
>  		    g->tm_hour, dt.hour);
> -  grub_test_assert (g->tm_mday == dt.day, "time %d bad day: %d vs %d", v,
> +  grub_test_assert (g->tm_mday == dt.day, "time %lld bad day: %d vs %d", (long long) v,
>  		    g->tm_mday, dt.day);
> -  grub_test_assert (g->tm_mon + 1 == dt.month, "time %d bad month: %d vs %d", v,
> +  grub_test_assert (g->tm_mon + 1 == dt.month, "time %lld bad month: %d vs %d",(long long) v,
>  		    g->tm_mon + 1, dt.month);
>    grub_test_assert (g->tm_year + 1900 == dt.year,
> -		    "time %d bad year: %d vs %d", v,
> +                   "time %lld bad year: %d vs %d", (long long) v,
>  		    g->tm_year + 1900, dt.year);
> -  grub_test_assert (g->tm_wday == w, "time %d bad week day: %d vs %d", v,
> +  grub_test_assert (g->tm_wday == w, "time %lld bad week day: %d vs %d", (long long) v,
>  		    g->tm_wday, w);
> +  grub_test_assert (back == v, "time %lld bad back transform: %lld", (long long) v,
> +                   (long long) back);
>  }
>
>  static void
>  date_test_iter (void)
>  {
> -  grub_int32_t tests[] = { -1, 0, +1, -2133156255, GRUB_INT32_MIN,
> +  grub_int32_t tests[] = { -1, 0, +1, 978224552, -2133156255, -2110094321, GRUB_INT32_MIN,
>  			   GRUB_INT32_MAX };

I think "tests" array update begs for a comment here and a blurb in the
commit message.

> +  /*
> +   * Test several known UNIX timestamps outside 32-bit time:
> +   *   1. 5774965200:  2152-12-31 21:00:00  - Leap year
> +   *   2. 4108700725:  2100-03-14 09:45:25  - Not a leap year
> +   *   3. -5029179792: 1810-08-19 21:36:48  - Not a leap year
> +   */
> +  grub_int64_t tests64[] = { (grub_int64_t) 5774965200,
> +                             (grub_int64_t) 4108700725,
> +                             (grub_int64_t) -5029179792 };
>    unsigned i;
>
>    for (i = 0; i < ARRAY_SIZE (tests); i++)
> @@ -71,6 +85,18 @@ date_test_iter (void)
>        date_test (x);
>        date_test (-x);
>      }
> +
> +  if (sizeof (time_t) > 4)
> +    {
> +      for (i = 0; i < ARRAY_SIZE (tests64); i++)
> +        date_test (tests64[i]);
> +      for (i = 0; i < 10000000; i++)
> +        {
> +          /* Ranges from 0064 to 6869. */

This "Ranges" is still not explained.

> +          grub_int64_t x = rand () + (rand () % 100 - 28) * (grub_uint64_t) GRUB_INT32_MAX;

Where 100 and 28 come from?

Daniel

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

Re: [PATCH v4 1/2] datetime: Support dates outside of 1901..2038 range

[Andrew Hamilton]

[-- Attachment #1.1: Type: text/plain, Size: 8481 bytes --]

I will make the requested changes tonight in a v5.

Just so I understand, is there some coding standard for preferring ternary
operators and comparing bools to true?

Thanks,
Andrew

On Tue, Aug 26, 2025 at 10:06 AM Daniel Kiper <daniel.kiper@oracle.com>
wrote:

> On Mon, Aug 25, 2025 at 10:17:37PM -0500, Andrew Hamilton wrote:
> > Support dates outside of 1901..2038.
> >
> > Fixes: https://savannah.gnu.org/bugs/?63894
> > Fixes: https://savannah.gnu.org/bugs/?66301
> >
> > Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
> > Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
> > ---
> >  grub-core/lib/datetime.c | 64 ++++++++++++++++++++++++++++++++--------
> >  include/grub/datetime.h  | 27 ++++++++++++-----
> >  2 files changed, 71 insertions(+), 20 deletions(-)
> >
> > diff --git a/grub-core/lib/datetime.c b/grub-core/lib/datetime.c
> > index 8f0922fb0..a0f84d989 100644
> > --- a/grub-core/lib/datetime.c
> > +++ b/grub-core/lib/datetime.c
> > @@ -64,7 +64,10 @@ grub_get_weekday_name (struct grub_datetime *datetime)
> >  #define SECPERDAY (24*SECPERHOUR)
> >  #define DAYSPERYEAR 365
> >  #define DAYSPER4YEARS (4*DAYSPERYEAR+1)
> > -
> > +/* 24 leap years in 100 years */
> > +#define DAYSPER100YEARS (100 * DAYSPERYEAR + 24)
> > +/* 97 leap years in 400 years */
> > +#define DAYSPER400YEARS (400 * DAYSPERYEAR + 97)
> >
> >  void
> >  grub_unixtime2datetime (grub_int64_t nix, struct grub_datetime
> *datetime)
> > @@ -76,10 +79,12 @@ grub_unixtime2datetime (grub_int64_t nix, struct
> grub_datetime *datetime)
> >    /* Convenience: let's have 3 consecutive non-bissextile years
> >       at the beginning of the counting date. So count from 1901. */
> >    int days_epoch;
> > -  /* Number of days since 1st Januar, 1901.  */
> > +  /* Number of days since 1st January, 1 (proleptic). */
> >    unsigned days;
> >    /* Seconds into current day.  */
> >    unsigned secs_in_day;
> > +  /* Tracks whether this is a leap year. */
> > +  bool is_bisextile;
> >
> >    /* Transform C divisions and modulos to mathematical ones */
> >    if (nix < 0)
> > @@ -92,27 +97,62 @@ grub_unixtime2datetime (grub_int64_t nix, struct
> grub_datetime *datetime)
> >      days_epoch = grub_divmod64 (nix, SECPERDAY, NULL);
> >
> >    secs_in_day = nix - days_epoch * SECPERDAY;
> > -  days = days_epoch + 69 * DAYSPERYEAR + 17;
> > +  /*
> > +   * 1970 is Unix Epoch. Adjust to a year 1 epoch:
> > +   *  Leap year logic:
> > +   *   - Years evenly divisible by 400 are leap years
> > +   *   - Otherwise, if divisible by 100 are not leap years
> > +   *   - Otherwise, if divisible by 4 are leap years
> > +   *  There are four 400-year periods (1600 years worth of days with
> leap days)
> > +   *  There are three 100-year periods worth of leap days (3*24)
> > +   *  There are 369 years in addition to the four 400 year periods
> > +   *  There are 17 leap days in 69 years (beyond the three 100 year
> periods)
> > +   */
> > +  days = days_epoch + 369 * DAYSPERYEAR + 17 + 24 * 3 + 4 *
> DAYSPER400YEARS;
> > +
> > +  datetime->year = 1 + 400 * (days / DAYSPER400YEARS);
> > +  days %= DAYSPER400YEARS;
> >
> > -  datetime->year = 1901 + 4 * (days / DAYSPER4YEARS);
> > +  /*
> > +   * On 31st December of bissextile (leap) years 365 days from the
> beginning
> > +   * of the year elapsed but year isn't finished yet - every 400 years
> > +   * 396 is 4 years less than 400 year leap cycle
> > +   * 96 is 1 day less than number of leap days in 400 years
> > +   */
> > +  if (days / DAYSPER100YEARS == 4)
> > +    {
> > +      datetime->year += 396;
> > +      days -= 396 * DAYSPERYEAR + 96;
> > +    }
> > +  else
> > +    {
> > +      datetime->year += 100 * (days / DAYSPER100YEARS);
> > +      days %= DAYSPER100YEARS;
> > +    }
> > +
> > +  datetime->year += 4 * (days / DAYSPER4YEARS);
> >    days %= DAYSPER4YEARS;
> > -  /* On 31st December of bissextile years 365 days from the beginning
> > -     of the year elapsed but year isn't finished yet */
> > +  /*
> > +   * On 31st December of bissextile (leap) years 365 days from the
> beginning
> > +   * of the year elapsed but year isn't finished yet - every 4 years
> > +   */
> >    if (days / DAYSPERYEAR == 4)
> >      {
> >        datetime->year += 3;
> > -      days -= 3*DAYSPERYEAR;
> > +      days -= 3 * DAYSPERYEAR;
> >      }
> >    else
> >      {
> >        datetime->year += days / DAYSPERYEAR;
> >        days %= DAYSPERYEAR;
> >      }
> > -  for (i = 0; i < 12
> > -      && days >= (i==1 && datetime->year % 4 == 0
> > -                   ? 29 : months[i]); i++)
> > -    days -= (i==1 && datetime->year % 4 == 0
> > -                         ? 29 : months[i]);
> > +
> > +  is_bisextile = datetime->year % 4 == 0
> > +                 && (datetime->year % 100 != 0 || datetime->year % 400
> == 0);
>
> Even if it works it is not fully correct...
>
> is_bisextile = (datetime->year % 4 == 0 &&
>                 (datetime->year % 100 != 0 || datetime->year % 400 == 0))
> ? true : false;
>
> > +  for (i = 0;
> > +       i < 12 && days >= ((i == 1 && is_bisextile == true) ? 29 :
> months[i]);
> > +       i++)
> > +    days -= ((i == 1 && is_bisextile == true) ? 29 : months[i]);
> >    datetime->month = i + 1;
> >    datetime->day = 1 + days;
> >    datetime->hour = (secs_in_day / SECPERHOUR);
> > diff --git a/include/grub/datetime.h b/include/grub/datetime.h
> > index bcec636f0..ff847e847 100644
> > --- a/include/grub/datetime.h
> > +++ b/include/grub/datetime.h
> > @@ -54,8 +54,9 @@ void grub_unixtime2datetime (grub_int64_t nix,
> >  static inline int
> >  grub_datetime2unixtime (const struct grub_datetime *datetime,
> grub_int64_t *nix)
> >  {
> > -  grub_int32_t ret;
> > +  grub_int64_t ret;
> >    int y4, ay;
> > +  bool is_bisextile;
> >    const grub_uint16_t monthssum[12]
> >      = { 0,
> >       31,
> > @@ -75,15 +76,11 @@ grub_datetime2unixtime (const struct grub_datetime
> *datetime, grub_int64_t *nix)
> >    const int SECPERHOUR = 60 * SECPERMIN;
> >    const int SECPERDAY = 24 * SECPERHOUR;
> >    const int SECPERYEAR = 365 * SECPERDAY;
> > -  const int SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
> > +  const grub_int64_t SECPER4YEARS = 4 * SECPERYEAR + SECPERDAY;
> >
> > -  if (datetime->year > 2038 || datetime->year < 1901)
> > -    return 0;
> >    if (datetime->month > 12 || datetime->month < 1)
> >      return 0;
> >
> > -  /* In the period of validity of unixtime all years divisible by 4
> > -     are bissextile*/
> >    /* Convenience: let's have 3 consecutive non-bissextile years
> >       at the beginning of the epoch. So count from 1973 instead of 1970
> */
> >    ret = 3 * SECPERYEAR + SECPERDAY;
> > @@ -94,13 +91,27 @@ grub_datetime2unixtime (const struct grub_datetime
> *datetime, grub_int64_t *nix)
> >    ret += y4 * SECPER4YEARS;
> >    ret += ay * SECPERYEAR;
> >
> > +  /*
> > +   * Correct above calculation (which assumes every 4 years is a leap
> year)
> > +   * to remove those "false leap years" that are divisible by 100 but
> not 400.
> > +   * Since this logic starts with seconds since 1973, 15 is used
> because:
> > +   *  - (1973 - 1) / 100 = 19 (floor due to integer math)
> > +   *  - (1973 - 1) / 400 = 4 (floor due to integer math)
> > +   *  - 19 - 4 - 15 = 0 (we want to start with no "false leap years" at
> time
> > +   *     zero of 1973)
> > +   */
> > +  ret -= ((datetime->year - 1) / 100 - (datetime->year - 1) / 400 - 15)
> > +         * SECPERDAY;
> > +
> >    ret += monthssum[datetime->month - 1] * SECPERDAY;
> > -  if (ay == 3 && datetime->month >= 3)
> > +  is_bisextile = ay == 3
> > +                 && (datetime->year % 100 != 0 || datetime->year % 400
> == 0);
>
> Again...
>
> is_bisextile = (ay == 3 && (datetime->year % 100 != 0 || datetime->year %
> 400 == 0)) ? true : false;
>
> > +  if (is_bisextile && datetime->month >= 3)
>
> is_bisextile == true && ...
>
> >      ret += SECPERDAY;
> >
> >    ret += (datetime->day - 1) * SECPERDAY;
> >    if ((datetime->day > months[datetime->month - 1]
> > -       && (!ay || datetime->month != 2 || datetime->day != 29))
> > +       && !(is_bisextile && datetime->month == 2 && datetime->day ==
> 29))
>
> is_bisextile == true && ...
>
> ... and I would drop "is_" from variable name...
>
> Daniel
>

[-- Attachment #1.2: Type: text/html, Size: 10697 bytes --]

[-- Attachment #2: Type: text/plain, Size: 141 bytes --]

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

Re: [PATCH v4 2/2] date_unit_test: test dates outside of 32-bit unix range

[Andrew Hamilton]

>  >  date_test_iter (void)
>  >  {
>  > -  grub_int32_t tests[] = { -1, 0, +1, -2133156255, GRUB_INT32_MIN,
>  > +  grub_int32_t tests[] = { -1, 0, +1, 978224552, -2133156255, -2110094321, GRUB_INT32_MIN,
>  >                          GRUB_INT32_MAX };
>
>  I think "tests" array update begs for a comment here and a blurb in the
>  commit message.
Will do, I'll make that update in a v5.


>  > +  if (sizeof (time_t) > 4)
>  > +    {
>  > +      for (i = 0; i < ARRAY_SIZE (tests64); i++)
>  > +        date_test (tests64[i]);
>  > +      for (i = 0; i < 10000000; i++)
>  > +        {
>  > +          /* Ranges from 0064 to 6869. */
>
>  This "Ranges" is still not explained.
>
>  > +          grub_int64_t x = rand () + (rand () % 100 - 28) * (grub_uint64_t) GRUB_INT32_MAX;
>
>  Where 100 and 28 come from?
@Vladimir Serbinenko  - do you happen to remember any background on
the year test range for this and the use of 100 / 28 in the
calculation? I tried to figure it out last night and the best I could
come up with was it was a big range that covers pretty much any
conceivable valid date - especially since the Gregorian calendar
really starts in the 1500s.

If not, I'll take another crack at understanding this tonight and add
some commentary for it in v5.

Thanks,
Andrew

On Tue, Aug 26, 2025 at 10:25 AM Daniel Kiper <daniel.kiper@oracle.com> wrote:
>
> On Mon, Aug 25, 2025 at 10:17:38PM -0500, Andrew Hamilton wrote:
> > Add tests outside the date range possible with 32-bit time
> > calculation.
> >
> > Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
> > Signed-off-by: Andrew Hamilton <adhamilt@gmail.com>
> > ---
> >  tests/date_unit_test.c | 44 +++++++++++++++++++++++++++++++++---------
> >  1 file changed, 35 insertions(+), 9 deletions(-)
> >
> > diff --git a/tests/date_unit_test.c b/tests/date_unit_test.c
> > index 99774f199..aec3dc3e4 100644
> > --- a/tests/date_unit_test.c
> > +++ b/tests/date_unit_test.c
> > @@ -25,12 +25,13 @@
> >  #include <grub/test.h>
> >
> >  static void
> > -date_test (grub_int32_t v)
> > +date_test (grub_int64_t v)
> >  {
> >    struct grub_datetime dt;
> >    time_t t = v;
> >    struct tm *g;
> >    int w;
> > +  grub_int64_t back = 0;
> >
> >    g = gmtime (&t);
> >
> > @@ -38,28 +39,41 @@ date_test (grub_int32_t v)
> >
> >    w = grub_get_weekday (&dt);
> >
> > -  grub_test_assert (g->tm_sec == dt.second, "time %d bad second: %d vs %d", v,
> > +  grub_datetime2unixtime (&dt, &back);
> > +
> > +  grub_test_assert (g->tm_sec == dt.second, "time %lld bad second: %d vs %d", (long long) v,
> >                   g->tm_sec, dt.second);
> > -  grub_test_assert (g->tm_min == dt.minute, "time %d bad minute: %d vs %d", v,
> > +  grub_test_assert (g->tm_min == dt.minute, "time %lld bad minute: %d vs %d", (long long) v,
> >                   g->tm_min, dt.minute);
> > -  grub_test_assert (g->tm_hour == dt.hour, "time %d bad hour: %d vs %d", v,
> > +  grub_test_assert (g->tm_hour == dt.hour, "time %lld bad hour: %d vs %d", (long long) v,
> >                   g->tm_hour, dt.hour);
> > -  grub_test_assert (g->tm_mday == dt.day, "time %d bad day: %d vs %d", v,
> > +  grub_test_assert (g->tm_mday == dt.day, "time %lld bad day: %d vs %d", (long long) v,
> >                   g->tm_mday, dt.day);
> > -  grub_test_assert (g->tm_mon + 1 == dt.month, "time %d bad month: %d vs %d", v,
> > +  grub_test_assert (g->tm_mon + 1 == dt.month, "time %lld bad month: %d vs %d",(long long) v,
> >                   g->tm_mon + 1, dt.month);
> >    grub_test_assert (g->tm_year + 1900 == dt.year,
> > -                 "time %d bad year: %d vs %d", v,
> > +                   "time %lld bad year: %d vs %d", (long long) v,
> >                   g->tm_year + 1900, dt.year);
> > -  grub_test_assert (g->tm_wday == w, "time %d bad week day: %d vs %d", v,
> > +  grub_test_assert (g->tm_wday == w, "time %lld bad week day: %d vs %d", (long long) v,
> >                   g->tm_wday, w);
> > +  grub_test_assert (back == v, "time %lld bad back transform: %lld", (long long) v,
> > +                   (long long) back);
> >  }
> >
> >  static void
> >  date_test_iter (void)
> >  {
> > -  grub_int32_t tests[] = { -1, 0, +1, -2133156255, GRUB_INT32_MIN,
> > +  grub_int32_t tests[] = { -1, 0, +1, 978224552, -2133156255, -2110094321, GRUB_INT32_MIN,
> >                          GRUB_INT32_MAX };
>
> I think "tests" array update begs for a comment here and a blurb in the
> commit message.
>
> > +  /*
> > +   * Test several known UNIX timestamps outside 32-bit time:
> > +   *   1. 5774965200:  2152-12-31 21:00:00  - Leap year
> > +   *   2. 4108700725:  2100-03-14 09:45:25  - Not a leap year
> > +   *   3. -5029179792: 1810-08-19 21:36:48  - Not a leap year
> > +   */
> > +  grub_int64_t tests64[] = { (grub_int64_t) 5774965200,
> > +                             (grub_int64_t) 4108700725,
> > +                             (grub_int64_t) -5029179792 };
> >    unsigned i;
> >
> >    for (i = 0; i < ARRAY_SIZE (tests); i++)
> > @@ -71,6 +85,18 @@ date_test_iter (void)
> >        date_test (x);
> >        date_test (-x);
> >      }
> > +
> > +  if (sizeof (time_t) > 4)
> > +    {
> > +      for (i = 0; i < ARRAY_SIZE (tests64); i++)
> > +        date_test (tests64[i]);
> > +      for (i = 0; i < 10000000; i++)
> > +        {
> > +          /* Ranges from 0064 to 6869. */
>
> This "Ranges" is still not explained.
>
> > +          grub_int64_t x = rand () + (rand () % 100 - 28) * (grub_uint64_t) GRUB_INT32_MAX;
>
> Where 100 and 28 come from?
>
> Daniel

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

Re: [PATCH v4 1/2] datetime: Support dates outside of 1901..2038 range

[Daniel Kiper via Grub-devel]

On Tue, Aug 26, 2025 at 10:28:08AM -0500, Andrew Hamilton wrote:
> I will make the requested changes tonight in a v5.
>
> Just so I understand, is there some coding standard for preferring ternary
> operators and comparing bools to true?

No, I have not seen one but I think if we have defined consts/enums/.. we
should use them instead of assuming that various operators/functions/...
will return what we expect. Though I am not against putting this into
GRUB Developers Manual.

Daniel

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

Re: [PATCH v4 1/2] datetime: Support dates outside of 1901..2038 range

[Andrew Hamilton]

[-- Attachment #1.1: Type: text/plain, Size: 743 bytes --]

Got it thank you, I’ll put taking a look at the dev manual for potential
updates on my mental todo list.

Thanks!
Andrew

On Tue, Aug 26, 2025 at 11:54 AM Daniel Kiper <daniel.kiper@oracle.com>
wrote:

> On Tue, Aug 26, 2025 at 10:28:08AM -0500, Andrew Hamilton wrote:
> > I will make the requested changes tonight in a v5.
> >
> > Just so I understand, is there some coding standard for preferring
> ternary
> > operators and comparing bools to true?
>
> No, I have not seen one but I think if we have defined consts/enums/.. we
> should use them instead of assuming that various operators/functions/...
> will return what we expect. Though I am not against putting this into
> GRUB Developers Manual.
>
> Daniel
>

[-- Attachment #1.2: Type: text/html, Size: 1131 bytes --]

[-- Attachment #2: Type: text/plain, Size: 141 bytes --]

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel