Starting with iOS 13 and macOS Catalina, the new Reminders app no longer supports CalDAV.
When you launch Reminders on iOS 13 or macOS 10.15 for the first time, you will be presented with an option to upgrade Reminders so that it may offer you newer and better functionality.
If you don't wish to use Reminders as your primary to-do app, and instead rely on BusyCal or a host of other 3rd party CalDAV task management apps, choosing Yes will migrate all your to-do-only calendars off of CalDAV and into a private silo run and managed solely by the new Reminders app.
Your to-do-only calendars, along with their contents, will in effect be deleted from BusyCal, as well as a host of other 3rd party CalDAV clients on all other platforms. If this has given you unwarranted confusion, stress and anxiety, or it wasn't immediately clear that upgrading Reminders would result in loss of data in every other CalDAV client, please leave them feedback. They listen.
After Reminders deletes your calendars and to-dos from CalDAV, it replaces these with a calendar named Reminders ⚠️ along with the following two entries inside, reminding you who to blame:
- Where are my reminders?
- The creator of this list has upgraded these reminders.
Choosing No on the other hand, will keep your calendars and to-dos intact, and these will continue to sync with all other CalDAV apps, including BusyCal. The only downside of this would be the inability to use newer features offered by the new Reminders app.
The only way to restore data would be to restore these from automatic backups BusyCal creates for you, on a timely basis. There is more on this here.
During migration, Reminders will also remove Calendar sharing from any calendars you were previously sharing with others. You will need to set these up again as explained here.
BusyCal automatically backs up your BusyCal database every day and saves your last 10 backups. If you wish to restore your calendar from one of these backups, select File > Restore BusyCal, select a backup file and then click Open. You'll be presented with a list of your calendars, check the calendars you want to restore, click Restore and they will be restored from the backup, overwriting their current contents.
Note: That any events that have been created or edited since the backup will be lost when you restore from the backup. If you don't want to restore an entire calendar and lose any recent changes that were made since the last backup, you can restore specific events from the backup as follows:
Create a new backup in BusyCal by selecting File > Create Backup.
Launch BusyCal while holding down the option key to display the Startup Options dialog, then select Start in Offline Mode and click Continue. When in offline mode BusyCal will not sync with iCloud, Google, Exchange or any other services.
Select File > Restore From Backup. Choose one of the recent backup files and click Open, then select the calendar that contains the events you wish to recover and and click Restore.
Find the missing events and drag them to your Desktop to create ics files of each.
Select File > Restore From Backup. Choose the most recent backup you created in step 1 and click Open, then check the same calendar you selected in step 4 and click Restore.
Double-click on the ics files you exported in step 5, or drag them into BusyCal, to import the events and place them on the appropriate calendar.
Quit/relaunch BusyCal to go back Online.
After importing your to-dos, if these got imported under "On My Mac" - that would be a local calendar on your machine, which won't sync to iCloud. You need to right-click on this calendar and choose the "Move to iCloud" option or manually select all to-dos in List view and drag them to the appropriate calendar under your iCloud account.
Once you restore your backup and BusyCal is able to push everything back the iCloud CalDAV server, your to-do only calendars will continue to sync without issues. Apple has only dropped support for CalDAV within the new Reminders app, their iCloud servers will continue to sync your calendars and to-dos between other CalDAV clients. 2Do app, for instance, has issued a similar explanation.
CalDAV is an open protocol used for managing all your calendaring events and to-dos, giving 1st party built-in apps no particular advantage over 3rd party apps. Apple has been a driving force behind this for decades, and so we don't see this going away. The rest of your calendars and events will be fine as they are.
However, it does look like they wanted to add a lot more functionality and features to the Reminders app, and given CalDAV as a protocol is limited in what it offers, they decided to drop support for CalDAV altogether. This isn't a bad thing, but this does mean you lose the capability of syncing your to-dos seamlessly between apps and platforms.
If you feel Apple should provide users with an option to sync this back to CalDAV, please leave them feedback.
Once you upgrade to the new Reminders app:
The new Reminders app will not sync with older macs and iOS devices, even between Reminders
The new Reminders app will not sync with BusyCal and vice versa as it has dropped support for CalDAV
There is currently no way of pushing data from BusyCal → the new Reminders app and vice versa.
To-dos added to BusyCal will show up on all CalDAV clients other than the new Reminders app, including older versions of Reminders