# Syncro — Verify appointment date day-of-week before creating **Rule:** Before creating any Syncro appointment, always verify that the computed date actually falls on the intended day of the week. **Why:** Day-of-week math is easy to get wrong. In the incident that prompted this rule (2026-05-21, ticket #32312), "Saturday" was computed as May 24 — which is actually a Sunday. The appointment landed on the wrong day and didn't appear where Winter expected it on the calendar. **How to verify:** Use Python or Bash to print the weekday before including it in the preview: ```bash py -c "import datetime; d = datetime.date(2026, 5, 24); print(d.strftime('%A %Y-%m-%d'))" # Output: Sunday 2026-05-24 ← would have caught the error ``` Or include the day name in the TICKET PREVIEW and require explicit user confirmation that the day-of-week matches their intent. **Catch:** Always show `Day YYYY-MM-DD` (e.g., "Saturday 2026-05-23") in the preview — never just the numeric date — so the user can verify at a glance. Reported by Winter, 2026-05-21.