diff --git a/tests/expected/time/gmtime.stdout b/tests/expected/time/gmtime.stdout
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..a5da960f12b9fa853d07e5e89fb37e545a3e7bae 100644
--- a/tests/expected/time/gmtime.stdout
+++ b/tests/expected/time/gmtime.stdout
@@ -0,0 +1,168 @@
+Unix epoch:
+ tm_sec = 0
+ tm_min = 0
+ tm_hour = 0
+ tm_mday = 1
+ tm_mon = 0
+ tm_year = 70
+ tm_wday = 4
+ tm_yday = 0
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+1970-03-01 00:00:00:
+ tm_sec = 0
+ tm_min = 0
+ tm_hour = 0
+ tm_mday = 1
+ tm_mon = 2
+ tm_year = 70
+ tm_wday = 0
+ tm_yday = 59
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+1970-12-31 23:59:59:
+ tm_sec = 59
+ tm_min = 59
+ tm_hour = 23
+ tm_mday = 31
+ tm_mon = 11
+ tm_year = 70
+ tm_wday = 4
+ tm_yday = 364
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+1972-02-29 23:59:59:
+ tm_sec = 59
+ tm_min = 59
+ tm_hour = 23
+ tm_mday = 29
+ tm_mon = 1
+ tm_year = 72
+ tm_wday = 2
+ tm_yday = 59
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+1972-12-31 23:59:59:
+ tm_sec = 59
+ tm_min = 59
+ tm_hour = 23
+ tm_mday = 31
+ tm_mon = 11
+ tm_year = 72
+ tm_wday = 0
+ tm_yday = 365
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+2000-02-29 23:59:59:
+ tm_sec = 59
+ tm_min = 59
+ tm_hour = 23
+ tm_mday = 29
+ tm_mon = 1
+ tm_year = 100
+ tm_wday = 2
+ tm_yday = 59
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+2000-12-31 23:59:59:
+ tm_sec = 59
+ tm_min = 59
+ tm_hour = 23
+ tm_mday = 31
+ tm_mon = 11
+ tm_year = 100
+ tm_wday = 0
+ tm_yday = 365
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+2100-03-01 00:00:00:
+ tm_sec = 0
+ tm_min = 0
+ tm_hour = 0
+ tm_mday = 1
+ tm_mon = 2
+ tm_year = 200
+ tm_wday = 1
+ tm_yday = 59
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+2100-12-31 23:59:59:
+ tm_sec = 59
+ tm_min = 59
+ tm_hour = 23
+ tm_mday = 31
+ tm_mon = 11
+ tm_year = 200
+ tm_wday = 5
+ tm_yday = 364
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+Year 2038, pre-i32 overflow:
+ tm_sec = 7
+ tm_min = 14
+ tm_hour = 3
+ tm_mday = 19
+ tm_mon = 0
+ tm_year = 138
+ tm_wday = 2
+ tm_yday = 18
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+Year 2038, post-i32 overflow:
+ tm_sec = 8
+ tm_min = 14
+ tm_hour = 3
+ tm_mday = 19
+ tm_mon = 0
+ tm_year = 138
+ tm_wday = 2
+ tm_yday = 18
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+Year 2106, pre-u32 overflow:
+ tm_sec = 15
+ tm_min = 28
+ tm_hour = 6
+ tm_mday = 7
+ tm_mon = 1
+ tm_year = 206
+ tm_wday = 0
+ tm_yday = 37
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
+
+Year 2106, post-u32 overflow:
+ tm_sec = 16
+ tm_min = 28
+ tm_hour = 6
+ tm_mday = 7
+ tm_mon = 1
+ tm_year = 206
+ tm_wday = 0
+ tm_yday = 37
+ tm_isdst = 0
+ tm_gmtoff = 0
+ tm_zone = UTC
diff --git a/tests/time/gmtime.c b/tests/time/gmtime.c
index f5a16f2af3deb0c01146a5c140a68391322a8d9f..da4bdb08d7a66ac6105644a5cdd7d1b91b68260e 100644
--- a/tests/time/gmtime.c
+++ b/tests/time/gmtime.c
@@ -5,17 +5,109 @@
#include "test_helpers.h"
+void print_tm(const struct tm *tm_ptr) {
+ printf(" tm_sec = %d\n", tm_ptr->tm_sec);
+ printf(" tm_min = %d\n", tm_ptr->tm_min);
+ printf(" tm_hour = %d\n", tm_ptr->tm_hour);
+ printf(" tm_mday = %d\n", tm_ptr->tm_mday);
+ printf(" tm_mon = %d\n", tm_ptr->tm_mon);
+ printf(" tm_year = %d\n", tm_ptr->tm_year);
+ printf(" tm_wday = %d\n", tm_ptr->tm_wday);
+ printf(" tm_yday = %d\n", tm_ptr->tm_yday);
+ printf(" tm_isdst = %d\n", tm_ptr->tm_isdst);
+ printf(" tm_gmtoff = %ld\n", tm_ptr->tm_gmtoff);
+ printf(" tm_zone = %s\n", tm_ptr->tm_zone);
+}
+
int main(void) {
- time_t a = 0;
- struct tm expected = { .tm_sec = 0, .tm_min = 0, .tm_hour = 0, .tm_mday = 1, .tm_year = 70,
- .tm_wday = 4, .tm_yday = 0, .tm_isdst = 0, .tm_gmtoff = 0, .tm_zone = "UTC" };
-
- struct tm *info = gmtime(&a);
- if (info->tm_sec != expected.tm_sec || info->tm_min != expected.tm_min ||
- info->tm_hour != expected.tm_hour || info->tm_mday != expected.tm_mday ||
- info->tm_year != expected.tm_year || info->tm_wday != expected.tm_wday ||
- info->tm_yday != expected.tm_yday || info->tm_isdst != expected.tm_isdst ||
- info->tm_gmtoff != expected.tm_gmtoff || strcmp(info->tm_zone, expected.tm_zone) != 0) {
- exit(EXIT_FAILURE);
- }
+ time_t unix_epoch_seconds = 0;
+
+ // Exercise the different branches of the leap year logic
+ // 1970: common year
+ time_t y1970_mar01_seconds = 5097600; // 1970-03-01 00:00:00
+ time_t y1970_dec31_seconds = 31535999; // 1970-12-31 23:59:59
+
+ // 1972: leap year
+ time_t y1972_feb29_seconds = 68255999; // 1972-02-29 23:59:59
+ time_t y1972_dec31_seconds = 94694399; // 1972-12-31 23:59:59
+
+ // 2000: leap year
+ time_t y2000_feb29_seconds = 951868799; // 2000-02-29 23:59:59
+ time_t y2000_dec31_seconds = 978307199; // 2000-12-31 23:59:59
+
+ // 2100: common year
+ time_t y2100_mar01_seconds = 4107542400; // 2100-03-01 00:00:00
+ time_t y2100_dec31_seconds = 4133980799; // 2100-12-31 23:59:59
+
+ // Year 2038-related corner cases
+ time_t y2038_pre_seconds = 2147483647;
+ time_t y2038_post_seconds = 2147483648;
+ time_t y2106_pre_seconds = 4294967295;
+ time_t y2106_post_seconds = 4294967296;
+
+ struct tm *result_tm = NULL;
+
+ puts("Unix epoch:");
+ result_tm = gmtime(&unix_epoch_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("1970-03-01 00:00:00:");
+ result_tm = gmtime(&y1970_mar01_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("1970-12-31 23:59:59:");
+ result_tm = gmtime(&y1970_dec31_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("1972-02-29 23:59:59:");
+ result_tm = gmtime(&y1972_feb29_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("1972-12-31 23:59:59:");
+ result_tm = gmtime(&y1972_dec31_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("2000-02-29 23:59:59:");
+ result_tm = gmtime(&y2000_feb29_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("2000-12-31 23:59:59:");
+ result_tm = gmtime(&y2000_dec31_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("2100-03-01 00:00:00:");
+ result_tm = gmtime(&y2100_mar01_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("2100-12-31 23:59:59:");
+ result_tm = gmtime(&y2100_dec31_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("Year 2038, pre-i32 overflow:");
+ result_tm = gmtime(&y2038_pre_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("Year 2038, post-i32 overflow:");
+ result_tm = gmtime(&y2038_post_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("Year 2106, pre-u32 overflow:");
+ result_tm = gmtime(&y2106_pre_seconds);
+ print_tm(result_tm);
+
+ puts("");
+ puts("Year 2106, post-u32 overflow:");
+ result_tm = gmtime(&y2106_post_seconds);
+ print_tm(result_tm);
}