The title says it all. That said I am not 100% sure that the changing from all-day to normal event caused the issue.
I’ve attached a sanitized version of the log. 0_1509284791897_log.txt
Hello,
I have just tried and I can’t reproduce the problem. Please specify as many details as possible, including exact steps to reproduce the problem, your calendar app, etc.
Sadly there are not many details to provide (I deleted the event in question and now the errors are gone).
I’ll try to recreate the situation tomorrow. What I can say is that I was using the stock calendar app on a Nexus 5 against a fastmail account (not sure if the latter is relevant though).
EDIT:// That said I cannot really find the code mentioned from the trace in https://gitlab.com/bitfireAT/ical4android/blob/master/src/main/java/at/bitfire/ical4android/AndroidEvent.kt – it seems the file changed a bit 
@apollo13 Seems like the calendar app has set the event to non-all-day, but didn’t set an EVENT_TIMEZONE, which is (as far as I understand it) required for non-all-day events.
This should not happen, but I have changed the code so that it at least doesn’t in this case (but use the system default time zone instead): https://gitlab.com/bitfireAT/ical4android/commit/c89046a96e11df682c146e28fbfbd5c5ccb93a80
I’ll send you an APK with the patch to test, too.
