Scheduled rules execute a hour after they are supposed to I have created a scheduled rule that sends a email based on a date field in nodes of a certain content type. The rule executes as scheduled and the email is sent but for some reason it only fires exactly a hour after its supposed to.

E.g on the admin/config/workflow/rules/schedule page the item is scheduled to execute at Thu, 2017-08-03 15:30 but I only receive the email at 16:30. 

I could fix this by adding a offset to the trigger time but I would rather want to understand why this is happening and fix the problem accordingly.
Cause 1:

After a rule is scheduled (using the Rules Scheduler submodule), it will only actually execute next time cron runs. Example:


schedule a rule to execute at timestamp X.
if the next time that cron runs is at Y mins after timestamp X, then the Rules execution will only happen then (= at Y mins after timestamp X).


Cause 2:

If your site is set to the correct timezone, but your users are set to a timezone that is 1 hour ahead, then that might also explain what's happening. In that case, correct the timezone accordingly.