Overridden AllDay events are not processed correctly
Use CalDav to reproduce this. Any CalDav client can be used that is hooked to a Yahoo Client (e.g iOS, OfficeSuite Mail, eM Client, etc.)
- Create a recurring AllDay event in the client and sync to server.
- Create an overridden occurrence (e.g open second occurrence and change the date).
- Sync.
Expected: The overridden occurrence is displayed correctly, e.g if it was moved from 26th Jan to 27th jan then it shouldn't be displayed on 26th Jan.
Currently: The overidden occurrence is displayed on both 26th and 27th jan.
Technical information: The Recurrence-Id in the example above is sent to Yahoo CalDav server as 26th jan, but the Yahoo server would return the same event iwth Recurrence-Id set to 27th jan.
Further complaint: I have noticed that the UI on the Yahoo Calendar displays this appropriately. It looks like you guys intentionally mess things up so the 3rd party clients connected to your server appear as buggy. We've got other "known bugs" caused by the same behavior - event data is returned malformed, but is processed properly internally on your end (but seen only on your UI).

Hi there, I’m sorry to hear that! We’d like to further investigate this, can you message us directly on Twitter at @YahooCare or on Facebook on our Yahoo Customer Care page? In case you do not have a social media account, please contact us at help.yahoo.com
Thank you!