Using Plan, message given:
Start time before the latest preceding fixed time Current time: 11:01 Last fixed time: 10:39 Are you sure?
Seems to be OK after I press Yes. Similar messages appear each time I press Begin for next activity.
I have many items listed, spanning several days (which I haven't tried before, but is currently my preferred way of using Plan (weekly rather than daily schedule as single file)).
this is a protection against setting current time (11:01) BEFORE the time of the preceding activity (is it 10:39?). Usually, this happens because of your error (e.g. 12:39 set wrongly instead of 11:39, when typing in manually). It is not an error only if 24 hours have passed and 11:01 is actually set on the next day. If you copy and pasted this message then it is surprising that current>last (which sounds ok).
there were no report of errors in those protections and they seem to work as designed
Plan is limited to a single working day (may misbehave if you do days longer than 30-40 hours)