A Scheduler appointment made in a timezone (e.g. GMT) for a future point after a change in timezone (e.g. the UK's recent change to BST) result in schedules being off by one hour.
Example: On the first of March, I make an appointment slot for the first of April at 9am, for one hour. On the 25th March in the UK, clocks are put forward one hour (changing from GMT to BST). From this point onward, the scheduled appointment looks like it has been made for 10am, not 9am.