[Bug #18922] Normalize time at 24:00:00 UTC

test/ruby/test_time.rb

@@ -53,6 +53,8 @@ class TestTime < Test::Unit::TestCase
     assert_raise_with_message(ArgumentError, msg) { Time.new(2021, 1, 1, "+09:99") }
     assert_raise_with_message(ArgumentError, msg) { Time.new(2021, 1, "+09:99") }
     assert_raise_with_message(ArgumentError, msg) { Time.new(2021, "+09:99") }
+
+    assert_equal([0, 0, 0, 2, 1, 2000], Time.new(2000, 1, 1, 24, 0, 0, "-00:00").to_a[0, 6])
   end
 
   def test_time_add()

time.c

@@ -654,6 +654,7 @@ static uint32_t month_arg(VALUE arg);
 static VALUE validate_utc_offset(VALUE utc_offset);
 static VALUE validate_zone_name(VALUE zone_name);
 static void validate_vtm(struct vtm *vtm);
+static void vtm_add_day(struct vtm *vtm, int day);
 static uint32_t obj2subsecx(VALUE obj, VALUE *subsecx);
 
 static VALUE time_gmtime(VALUE);
@@ -2032,6 +2033,12 @@ vtm_add_offset(struct vtm *vtm, VALUE off, int sign)
         vtm->hour = hour;
     }
 
+    vtm_add_day(vtm, day);
+}
+
+static void
+vtm_add_day(struct vtm *vtm, int day)
+{
     if (day) {
         if (day < 0) {
             if (vtm->mon == 1 && vtm->mday == 1) {
@@ -2393,6 +2400,13 @@ time_init_args(rb_execution_context_t *ec, VALUE time, VALUE year, VALUE mon, VA
 
     if (utc == UTC_ZONE) {
         tobj->timew = timegmw(&vtm);
+        if (vtm.hour == 24) { /* special case: 24:00:00 only */
+            /* Since no need to take care of DST in UTC, just reset
+             * hour and advance date, not to discard the validated
+             * vtm. */
+            vtm.hour = 0;
+            vtm_add_day(&vtm, 1);
+        }
         tobj->vtm = vtm;
         tobj->tm_got = 1;
         TZMODE_SET_UTC(tobj);