After calendar sync is set you can click on Calendar Sync button to see Last Sync Date, currently synced filters, and options to update synced filters or add another external calendar. Last Sync Date shows the timestamp of the last request received from your personal calendar. If this timestamp is older than 48 hours it means that your personal calendar may be not up to date. You should re-sync your personal calendar to ensure the event updates keep flowing (by repeating the sync setup steps).
...
To update, apply new filters to select the new set of events. After the update currently To update your filters and add new project events to your calendar, click on the Filters button (next to the Calendar View in the top menu tabs). The Filter menu will appear (as below). You can then select a new set of events.
...
Once finished, click on the Sync Settings button at the right, and then click on the Update button.
A message will appear (as above), confirming that you wish to replace your existing filters with the new ones you just selected. After you click Update, the current synced filters will be replaced by the newly applied filters . Your personal calendar will receive this new event set at and new events matching those criteria will be automatically added to your calendar during the next sync.
...