What Does OneCal Sync?

OneCal keeps a limited window of events in sync at a time to ensure reliable performance. This page explains which events are synced, and which ones are intentionally left out.

How far into the future does OneCal sync?

OneCal syncs events up to 1 year ahead for Google and iCloud calendars, and up to 3 months ahead for Outlook calendars.

Events scheduled beyond these ranges may not sync consistently. The time window updates automatically as time progresses, so events sync as they come within range, without you having to do anything. These windows exist to maintain reliability, as there is a limit to how many events OneCal can keep in sync without running into issues with the underlying calendar provider.

Does OneCal sync past events?

No. If your past events are not syncing to another calendar, this is expected behavior. OneCal is mainly intended for keeping your current and future availability in sync across calendars, and is not intended for syncing historical events. Since the number of events OneCal can keep in sync is limited, we prioritize current and future events.

Recurring events that extend into the future also sync in the past, but individual events that only exist in the past are not synced.

Are changes to clone events synced back to the original?

No. Changes you make to a clone event are never propagated back to the original event. This aligns with one of our core principles: never modifying your original events.

Clone events can be safely modified, since any change to them is reversible: clone events can be removed from your calendars and re-created without consequences, even if something goes wrong. Changes to your original events, however, can have lasting impacts if other guests are involved. For this reason, we currently have no plans to sync changes from clone events back to the original events.

Does OneCal clone its own clone events?

No. OneCal marks every clone event it creates, and skips those events when it reads a calendar for events to sync. Only your original events are ever cloned.

This means calendar syncs pointing in opposite directions are safe to combine. If you sync Work -> Personal and also sync Personal -> Work, the clone event that lands in your personal calendar is not picked up as an original event by the second calendar sync, so it is never copied back to work. Events cannot bounce between your calendars, and no loop can build up over time.

The same applies to a multi-way calendar sync across three or more calendars: each original event produces exactly one clone event per other calendar, and those clone events never produce clone events of their own.