diff --git a/lib/icinga/legacytimeperiod.cpp b/lib/icinga/legacytimeperiod.cpp
index d8355110f..33e666544 100644
--- a/lib/icinga/legacytimeperiod.cpp
+++ b/lib/icinga/legacytimeperiod.cpp
@@ -586,13 +586,35 @@ Array::Ptr LegacyTimePeriod::ScriptFunc(const TimePeriod::Ptr& tp, double begin,
 	Dictionary::Ptr ranges = tp->GetRanges();
 
 	if (ranges) {
-		for (int i = 0; i <= (end - begin) / (24 * 60 * 60); i++) {
-			time_t refts = begin + i * 24 * 60 * 60;
-			tm reference = Utility::LocalTime(refts);
+		tm tm_begin = Utility::LocalTime(begin);
+
+		// Always evaluate time periods for full days as their ranges are given per day.
+		tm_begin.tm_hour = 0;
+		tm_begin.tm_min = 0;
+		tm_begin.tm_sec = 0;
+		tm_begin.tm_isdst = -1;
+
+		// Helper to move a struct tm to midnight of the next day for the loop below.
+		// Due to DST changes, this may move the time by something else than 24 hours.
+		auto advance_to_next_day = [](tm *t) {
+			t->tm_mday++;
+			t->tm_hour = 0;
+			t->tm_min = 0;
+			t->tm_sec = 0;
+			t->tm_isdst = -1;
+
+			// Normalize fields using mktime.
+			mktime(t);
+
+			// Reset tm_isdst so that future calls figure out the correct time zone after setting tm_hour/tm_min/tm_sec.
+			t->tm_isdst = -1;
+		};
+
+		for (tm reference = tm_begin; mktime_const(&reference) <= end; advance_to_next_day(&reference)) {
 
 #ifdef I2_DEBUG
 			Log(LogDebug, "LegacyTimePeriod")
-				<< "Checking reference time " << refts;
+				<< "Checking reference time " << mktime_const(&reference);
 #endif /* I2_DEBUG */
 
 			ObjectLock olock(ranges);