Bad UX
From RonWareWiki
Bad UX case study #1: Google Calendar (GC)
GC is a “cloud-based” calendar application, hosted by Google. It lets you set appointments using your web-browser, and has a relatively rich and easy-to-use user-interface. Among its many features are the ability to “invite” others to your appointments, and the ability to synchronize your calendar between the “cloud” and your mobile devices.
The “bad UX (user-experience)” occurs when your device decides that DST (daylight savings time) has ended or begun. Any appointments entered prior to that change will suddenly be an hour behind or forward (depending on whether DST has started or ended). Suddenly one finds that the dentist appointment is at 07:30 instead of 08:30, which is embarrassing at least; worse is when one finds that the meeting with the auditor is at 12:00 instead of 11:00...
This UX flaw means one cannot rely upon GC unless one takes certain measures.
The logic GC uses is that when you create an appointment, it converts the time into GMT. So the appointment you set for “08:00” is (say) stored as being at “01:00”. Now when your local device changes DST, the time of the appointment does *not* change, but the way it is displayed (and the times of any alarms it's set) are changed accordingly. You now have a “07:00” appointment. This is extremely poor UX, and I'm surprised that Google has not paid attention to the many complaints (back to at last 2009) about this misfeature.
If you wish to continue using GC, the only measure you can take to prevent this from messing with your appointments and causing you to lose sleep and/or business is to change your time to GMT (no DST) in the “cloud” version, and to subsequently change your time to GMT+0 in all your connected devices' GC applications. Note that when you make this change in the “cloud”, all your appointments' times will change — you will need to manually adjust them. Subsequent to that, you’ll need to resynchronize your devices so they show the correct appointment times.