In Google Calendar each event has an identifier. This identifier is used to see which events are the same. E.g. when Google Calendar reports that there was a change in event "A" CalenGoo checks if it already knows event "A" and then either modifies the existing event "A" or creates a new event if it didn’t know event "A" yet.

Unfortunately Google slightly changed the IDs of all events about three days ago. Since then when CalenGoo downloaded a changed event from Google Calendar it couldn’t recognize that it was a changed event. Instead it thought it would be a new event because it didn’t know that ID yet. This results in a duplicate of that event being displayed in CalenGoo (but not in Google Calendar). With the next update CalenGoo will handle this situation correctly and will know which IDs (old and new) are the same. The update has already been uploaded to Apple and will probably be released in a few days.

However there is a way how you can fix the problem immediately: You just have to let CalenGoo download all events again so that it knows the new IDs. To do this there are two options:

1. Tap "Settings", "Reset calendars" in CalenGoo to erase all events and calendars in CalenGoo and re-download everything from Google Calendar during the next sync.
2. If only a single calendar is affected by this problem, you can tap on "Settings", "Debug Tools", "Calendars", "the affected calendar", "Re-download" and sync afterward. This way all events of that calendar will be erased from CalenGoo’s database and re-downloaded during the next sync.
3. Switch to syncing via OAuth2 (see below).

However before trying one of these solutions you have to ensure that all your events are in Google Calendar ( http://calendar.google.com ) because both solutions will delete all events from CalenGoo’s database and then they will redownload everything from Google Calendar. It is also a good idea to download a backup of your Google Calendar from time to time. Just open http://calendar.google.com on your computer, sign in, click on the gear icon in the upper right corner and then on "Settings", "Calendars", "Export calendars".

This problem affects only users who synced via email/password or AuthSub. It didn’t affect users syncing via "OAuth2".

Switch to syncing via OAuth2

Just follow these steps to switch to syncing via OAuth2.

1. Ensure that *all* your events and tasks are in Google Calendar ( http://calendar.google.com ). If necessary enter any missing events, tasks or changes manually in Google Calendar. You can see which events haven't been uploaded yet under "Settings", "Debug Tools", "Changes to upload".
2. Tap "Settings", "Login screen" in CalenGoo. Then tap the gear icon in the lower right corner and choose "OAuth2 Login". Follow the instructions and wait for the sync to finish. It will erase all events and tasks in CalenGoo and re-download everything from Google.
3. It might be necessary to tap "Settings", "Debug Tools", "Reset Tasks" if you synced tasks before. And please ensure that "Settings", "Tasks", "Use login credentials" is turned on if you sync tasks.

When syncing this way, it will use the "new" Google Calendar colors for your calendars and events. If you would like to change the color of a calendar just tap the blue button behind the calendar's name under "Settings", "Visibility/Download" in CalenGoo.