Skip impossible UTC dates in sparse cron searches

Parsing a schedule once removes most repeated work, but an annual
schedule can still block the event loop during time-zone formatting.
Reject impossible UTC minutes and dates before calling Intl. Retain
localized hour matching and invalid-date errors.

Verified the reproduced formatting-budget regression and focused
scheduler, routine, and SQL eligibility tests. The PR preserves the
earlier failed timing acceptance and tracks the final live run.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

doc/DEVELOPING.md

@@ -1458,7 +1458,7 @@ the dispatch time of a known future deadline. Failed scans retry at that same
 interval. Future timers do not hold idle work open, and standby, idle drain and
 shutdown retain the coordinator's admission gates. External database writers
 rely on the periodic recovery scan. Sparse cron searches reuse one parsed
-expression so repeated parsing cannot block unrelated deadlines.
+expression and skip impossible UTC dates before localized formatting.
 
 Keep relevant heartbeat extractions and their focused tests in `server/src/services/heartbeat/`.
 Follow [Heartbeat execution boundaries](../rules/heartbeat-execution-boundaries.mdc)

server/src/services/routines-formatter-cache.test.ts

@@ -20,6 +20,24 @@ describe("nextCronTickInTimeZone formatter caching", () => {
     expect(parses).toBe(1);
   });
 
+  it("skips impossible UTC dates before localized formatting", () => {
+    const format = Intl.DateTimeFormat.prototype.formatToParts;
+    let formats = 0;
+    vi.spyOn(Intl.DateTimeFormat.prototype, "formatToParts").mockImplementation(function(this: Intl.DateTimeFormat, date) {
+      formats++;
+      if (formats > 48) throw new Error("Sparse UTC schedules must skip impossible dates");
+      return format.call(this, date);
+    });
+    const next = nextCronTickInTimeZone("0 12 1 1 *", "UTC", new Date("2020-01-01T12:00:00Z"));
+    expect(next?.toISOString()).toBe("2021-01-01T12:00:00.000Z");
+    expect(formats).toBeLessThanOrEqual(48);
+  });
+
+  it.each(["UTC", "America/New_York"])("rejects invalid search dates in %s", timeZone => {
+    expect(() => nextCronTickInTimeZone("0 12 1 1 *", timeZone, new Date(Number.NaN)))
+      .toThrow(RangeError);
+  });
+
   it("computes the next occurrence of a sparse monthly cron correctly", () => {
     const next = nextCronTickInTimeZone(
       "30 6 1 * *",

server/src/services/routines.ts

@@ -255,6 +255,12 @@ function getZonedMinuteParts(date: Date, timeZone: string) {
 }
 
 function matchesCronMinute(cron: ReturnType<typeof parseCron>, timeZone: string, date: Date) {
+  if (timeZone === "UTC" && Number.isFinite(date.getTime()) && (
+    !cron.minutes.includes(date.getUTCMinutes())
+    || !cron.daysOfMonth.includes(date.getUTCDate())
+    || !cron.months.includes(date.getUTCMonth() + 1)
+    || !cron.daysOfWeek.includes(date.getUTCDay())
+  )) return false;
   const parts = getZonedMinuteParts(date, timeZone);
   return (
     cron.minutes.includes(parts.minute) &&