Outlook can't handle timezones
So a colleague in Germany has just booked a 4-day event on Outlook: that is , from Tuesday to Friday. But because of differences in time zones, this has translated to us guys in Britain (an hour behind, see) as from 23:00 on Monday to 23:00 on Friday -- thereby flagging it up as a 5-day event, because although only actually registering as an our of Monday, it actually books it as the entire day. If I hadn't been sharp-eyed enough here, I would have turned up a day early, something I really do not want to do by mistake.
Serious D'oh! moment
I actually wonder how Google Calendar handles it. Does it have special treatment for 'all day' events? I assume so since it's a dedicated tickbox that removes the option of entering specific times...
Based on the .ics, a regular event looks like this:
An all-day event looks like this:
Also (probably due to the same reason) Outlook cannot handle local-time events (which should not move when you switch timezones) like alarm clock reminders.
When you import a local-time event from ICS file, Outlook will convert it to the timezone you are in at the moment when you import it. When you later change your timezone and import it again, you have it twice.
You can many bad things about Thunderbird's calendar app (Lightning), but whole-day events and local-time events work fine there...
Unless the .ics specifies a time zone, I don't see how Outlook could divine which timezone it's supposed to be in, especially when you're changing time zones on it.