If the timezone of a calendar is changed to one covered by the daylight savings, the calendar displays a wrong set of events in the months that the changes occur.

Steps to reproduce

1. Create a calendar with a timezone like America/New York (-0400), for example;
2. Set some recurring weekly events on it (Calendar1.png);
3. Create a subscription for this Calendar;
4. Rearrange the events on the Calendar by moving them to different days (Calendar2.png);
5. Change the timezone to America/Sao Paulo (-0200).

Expected behavior
Nothing changes besides the timezone.

Actual behavior
The events on the Calendar are rearranged and some of them are now displayed incorrectly (Calendar3.png).
At this point, if you start changing the order of events again, all the Calendar subscriptions will show what it seems to be an out of sync content.
Even if you were to revert the timezone setting back, the Calendar subscriptions won't get fixed, nor will the Calendar on Confluence.