Thunderbird version: 52.4.0
OS: Linux Mint: 17.3
Steps to reproduce:
- Create an all-day event (with no specific time). It appears in the upper part of the calendar.
- Open the all-day event and uncheck the property "All day event". The current time is displayed.
- Save the modified event. The event appears for a second at the current time in calendar.
- After a second date and time switches to following setting
From: , 12am
To: , 12am
Thanks
Juergen