diff --git a/src/run/run.c b/src/run/run.c
index 6a0b0d78b98..babd9027e49 100644
--- a/src/run/run.c
+++ b/src/run/run.c
@@ -382,21 +382,22 @@ static int parse_argv(int argc, char *argv[]) {
 
                 case ARG_ON_CALENDAR: {
                         _cleanup_(calendar_spec_freep) CalendarSpec *cs = NULL;
-                        usec_t next, curr;
 
                         /* Let's make sure the given calendar event is not in the past */
-                        curr = now(CLOCK_REALTIME);
                         r = calendar_spec_from_string(optarg, &cs);
                         if (r < 0)
-                                return log_error_errno(r, "Failed to parse calendar event specification");
-                        r = calendar_spec_next_usec(cs, curr, &next);
-                        if (r < 0) {
-                                /* The calendar event is in the past - in such case
-                                 * don't add an OnCalendar property and execute
-                                 * the command immediately instead */
-                                log_warning("Specified calendar event is in the past, executing immediately");
-                                break;
-                        }
+                                return log_error_errno(r, "Failed to parse calendar event specification: %m");
+
+                        r = calendar_spec_next_usec(cs, now(CLOCK_REALTIME), NULL);
+                        if (r == -ENOENT)
+                                /* The calendar event is in the past - let's warn about this, but install it
+                                 * anyway as it is. The service manager will trigger the service right-away
+                                 * then, but everything is discoverable as usual. Moreover, the server side
+                                 * might have a different clock or timezone than we do, hence it should
+                                 * decide when or whether to run something. */
+                                log_warning("Specified calendar expression is in the past, proceeding anyway.");
+                        else if (r < 0)
+                                return log_error_errno(r, "Failed to calculate next time calendar expression elapses: %m");
 
                         r = add_timer_property("OnCalendar", optarg);
                         if (r < 0)
diff --git a/src/shared/calendarspec.c b/src/shared/calendarspec.c
index 6e318fa265f..4365dbaca88 100644
--- a/src/shared/calendarspec.c
+++ b/src/shared/calendarspec.c
@@ -1193,6 +1193,8 @@ static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
         int tm_usec;
         int r;
 
+        /* Returns -ENOENT if the expression is not going to elapse anymore */
+
         assert(spec);
         assert(tm);
 
@@ -1285,14 +1287,13 @@ static int find_next(const CalendarSpec *spec, struct tm *tm, usec_t *usec) {
         }
 }
 
-static int calendar_spec_next_usec_impl(const CalendarSpec *spec, usec_t usec, usec_t *next) {
+static int calendar_spec_next_usec_impl(const CalendarSpec *spec, usec_t usec, usec_t *ret_next) {
         struct tm tm;
         time_t t;
         int r;
         usec_t tm_usec;
 
         assert(spec);
-        assert(next);
 
         if (usec > USEC_TIMESTAMP_FORMATTABLE_MAX)
                 return -EINVAL;
@@ -1310,7 +1311,9 @@ static int calendar_spec_next_usec_impl(const CalendarSpec *spec, usec_t usec, u
         if (t < 0)
                 return -EINVAL;
 
-        *next = (usec_t) t * USEC_PER_SEC + tm_usec;
+        if (ret_next)
+                *ret_next = (usec_t) t * USEC_PER_SEC + tm_usec;
+
         return 0;
 }
 
@@ -1319,12 +1322,14 @@ typedef struct SpecNextResult {
         int return_value;
 } SpecNextResult;
 
-int calendar_spec_next_usec(const CalendarSpec *spec, usec_t usec, usec_t *next) {
+int calendar_spec_next_usec(const CalendarSpec *spec, usec_t usec, usec_t *ret_next) {
         SpecNextResult *shared, tmp;
         int r;
 
+        assert(spec);
+
         if (isempty(spec->timezone))
-                return calendar_spec_next_usec_impl(spec, usec, next);
+                return calendar_spec_next_usec_impl(spec, usec, ret_next);
 
         shared = mmap(NULL, sizeof *shared, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
         if (shared == MAP_FAILED)
@@ -1352,8 +1357,8 @@ int calendar_spec_next_usec(const CalendarSpec *spec, usec_t usec, usec_t *next)
         if (munmap(shared, sizeof *shared) < 0)
                 return negative_errno();
 
-        if (tmp.return_value == 0)
-                *next = tmp.next;
+        if (tmp.return_value == 0 && ret_next)
+                *ret_next = tmp.next;
 
         return tmp.return_value;
 }