# Forward-trim

Source: https://lemon.cy/glossary/forward-trim/  
Publisher: Lemon.cy (Red Tribe Media Ltd, Limassol, Cyprus)  
Updated: 2026-09-10 · Verified against production: 2026-09-10

**Short answer:** Booking.com re-exporting an in-progress stay with its elapsed nights removed, so the event's start date walks forward one night at a time while the checkout stays fixed. Lemon pins the original check-in: an arrival that has already happened is immutable.

Forward-trims are the single most frequent thing a Booking.com feed does. Because the trim happens on almost every export, Lemon sees it on almost every five-minute fetch of every in-progress stay: 1,240 `elapsed_checkin_pinned` decisions between 2026-09-05 and 2026-09-10.

Before Lemon's identity rules, a forward-trim was interpreted as a date change (job reset, cleaner messaged) or, where an identifier included the check-in date, as a disappearance (job cancelled, then recreated five minutes later). Rule 3 — an already-elapsed check-in is immutable for every feed — and rule 4 — only the checkout drives the clean — remove both effects.

## Related

- [Re-key](https://lemon.cy/glossary/re-key/)
- [Checkout-driven scheduling](https://lemon.cy/glossary/checkout-driven-scheduling/)
- [Why does a Booking.com iCal booking's check-in date move forward every day during the stay?](https://lemon.cy/learn/forward-trim-booking-com-in-progress-stay/)