# Sync window

Kalender Sync syncs events within a window: **3 months into the past** for everyone — **into the future depending on your plan: 6 months (Free & Basic) or 18 months (Professional)**. It's shown as a timeline when you set up a sync. The window moves along every day.

## Why a window at all?

- **Data minimisation**: events from two years ago don't block anyone anymore — transferring them would be unnecessary data processing.
- **Performance**: even very full calendars (thousands of events) stay fast to sync.

## What that means in practice

- An event **8 months out**: on Free and Basic it's missing from the target at first — that's normal. As soon as it moves into the 6-month window, it appears **automatically**, nothing to do on your side. On Professional it's already synced, since it sits within the 18-month window.
- **Old events** (older than 3 months) aren't transferred — on the initial sync this sometimes surprises ("where's last year?"), but it's intentional.
- For [recurring events](https://docs.kalender-sync.de/en/sync/recurring-events/), the target holds the occurrences within the window; further ones follow automatically.

## Can the window be changed?

The Professional plan already extends the forward window to **18 months** — for bookings far ahead (e.g. 9 months), that's the direct route. Beyond that, a freely configurable window per sync remains planned ([Known limitations](https://docs.kalender-sync.de/en/troubleshooting/known-limitations/)). If a concrete case blocks you, [let us know](https://docs.kalender-sync.de/en/troubleshooting/contact-support/) — it helps us prioritise.