diff --git a/src/shared/calendarspec.c b/src/shared/calendarspec.c
index 5fdae235366..01bc10f97ec 100644
--- a/src/shared/calendarspec.c
+++ b/src/shared/calendarspec.c
@@ -1235,14 +1235,43 @@ static bool matches_weekday(int weekdays_bits, const struct tm *tm, bool utc) {
         return (weekdays_bits & (1 << k));
 }
 
+static int tm_compare(const struct tm *t1, const struct tm *t2) {
+        int r;
+
+        assert(t1);
+        assert(t2);
+
+        r = CMP(t1->tm_year, t2->tm_year);
+        if (r != 0)
+                return r;
+
+        r = CMP(t1->tm_mon, t2->tm_mon);
+        if (r != 0)
+                return r;
+
+        r = CMP(t1->tm_mday, t2->tm_mday);
+        if (r != 0)
+                return r;
+
+        r = CMP(t1->tm_hour, t2->tm_hour);
+        if (r != 0)
+                return r;
+
+        r = CMP(t1->tm_min, t2->tm_min);
+        if (r != 0)
+                return r;
+
+        return CMP(t1->tm_sec, t2->tm_sec);
+}
+
 /* A safety valve: if we get stuck in the calculation, return an error.
  * C.f. https://bugzilla.redhat.com/show_bug.cgi?id=1941335. */
 #define MAX_CALENDAR_ITERATIONS 1000
 
 static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
         struct tm c;
-        int tm_usec;
-        int r;
+        int tm_usec, r;
+        bool invalidate_dst = false;
 
         /* Returns -ENOENT if the expression is not going to elapse anymore */
 
@@ -1255,7 +1284,8 @@ static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
         for (unsigned iteration = 0; iteration < MAX_CALENDAR_ITERATIONS; iteration++) {
                 /* Normalize the current date */
                 (void) mktime_or_timegm_usec(&c, spec->utc, /* ret= */ NULL);
-                c.tm_isdst = spec->dst;
+                if (!invalidate_dst)
+                        c.tm_isdst = spec->dst;
 
                 c.tm_year += 1900;
                 r = find_matching_component(spec, spec->year, &c, &c.tm_year);
@@ -1345,6 +1375,18 @@ static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
                 if (r == 0)
                         continue;
 
+                r = tm_compare(tm, &c);
+                if (r == 0) {
+                        assert(tm_usec + 1 <= 1000000);
+                        r = CMP(*usec, (usec_t) tm_usec + 1);
+                }
+                if (r >= 0) {
+                        /* We're stuck - advance, let mktime determine DST transition and try again. */
+                        invalidate_dst = true;
+                        c.tm_hour++;
+                        continue;
+                }
+
                 *tm = c;
                 *usec = tm_usec;
                 return 0;
diff --git a/src/test/test-calendarspec.c b/src/test/test-calendarspec.c
index 005d9b0771b..e8c50ead9f7 100644
--- a/src/test/test-calendarspec.c
+++ b/src/test/test-calendarspec.c
@@ -47,7 +47,7 @@ static void _test_next(int line, const char *input, const char *new_tz, usec_t a
         if (old_tz)
                 old_tz = strdupa_safe(old_tz);
 
-        if (!isempty(new_tz))
+        if (!isempty(new_tz) && !strchr(new_tz, ','))
                 new_tz = strjoina(":", new_tz);
 
         assert_se(set_unset_env("TZ", new_tz, true) == 0);
@@ -219,6 +219,8 @@ TEST(calendar_spec_next) {
         /* Check that we don't start looping if mktime() moves us backwards */
         test_next("Sun *-*-* 01:00:00 Europe/Dublin", "", 1616412478000000, 1617494400000000);
         test_next("Sun *-*-* 01:00:00 Europe/Dublin", "IST", 1616412478000000, 1617494400000000);
+        /* Europe/Dublin TZ that moves DST backwards */
+        test_next("hourly", "IST-1GMT-0,M10.5.0/1,M3.5.0/1", 1743292800000000, 1743296400000000);
 }
 
 TEST(calendar_spec_from_string) {