There are two different ways to integrate OS calendars into TimeTree.
1: Synchronizing calendars using 'My Schedule/All Calendars'
TimeTree has a section that displays multiple calendars, including your OS calendars named "My Schedule/All Calendars". For more information about "My Schedule/All Calendars", click here.
Please note that you can not sync an OS calendar with a TimeTree shared calendar.
You can view OS calendar appointments in the "My schedule/All Calendars" view of TimeTree. If you update, change or edit events within your OS calendars, changes made will automatically be reflected within the "My schedule/All Calendars" view.
You can edit and change events imported from your OS calendar within the TimeTree app, however as the sync process is one way only OS calendar events edited and changed within the TimeTree App are not relfected in your OS calendar.
2: Importing calendars into specific calendars
By importing OS calendars into your TimeTree calendar, you and the members of a shared calendar can view, edit, and delete events to meet everyone's needs.
After importing an OS calendar onto TimeTree, we highly recommend creating future events manually within TimeTree, rather than importing repetitively, as this may cause the TimeTree calendar to create duplicate existing events.
Changes made in your TimeTree calendar do not affect your OS calendar.
Please note that this is a one-way sync from your OS calendar to your TimeTree Calendar, meaning that changes made within TimeTree are not reflected on the original OS calendar.
For more information on how to copy OS calendars,Click here.