Access calendar sync from the Calendar page by tapping the sync icon (🔄) in the header, or from Calendar Settings. You can import events from your Apple Calendar (iOS/Android) or Google Calendar (web). Large imports are processed in batches to keep the app responsive.
Example
If you have hundreds of events, the import will show progress (e.g., "Importing 50/200") and you can cancel if needed. The app processes events in batches of 50 to ensure smooth performance.