### Steps to reproduce

* We had [a recurring meeting](https://community.openproject.org/projects/communicator-stream/recurring_meetings/33) scheduled for 11h30 EAT.

* This would have corresponded to to 9h30 CET at the time of creation, since it was created before we entered summer time.

* One we entered summer time, it should have shown 10h30 CEST; however, the meeting start time showed up as 11h30 CET.

* This is off by two hours. This difference is correct in the original state but not when we're observing Summer time in Surope. It should be a difference of one hour now.

* When I try to edit the meeting template (from Germany), the base time shows CET.

* I changed the start time from 11h30 to 9h and pressed save.

* Because the original time is in CET, it then saves it as 10h CEST (and 11h EAT).


### What is the buggy behavior?

* The original meeting series was off by two hours instead of one as expected (EAT and CEST have a one hour difference).

* When editing a meeting set in EAT, it shows me the original time in CET


### What is the expected behavior?

* A meeting set to start at a certain time (11h30 EAT) was 9h30 CET before summer time; with summer time, the difference should be reduced to 1 hour and not 2.

* The original meeting should have been set for 10h30 CEST.

* When editing a meeting set in a different time zone, Begin of the insertionwe show form fields inEnd of the insertion Begin of the deletion if we're showingEnd of the deletion the time Begin of the insertionzone the meeting was created in, not your own current time zone.

* A banner is shown indicating that it differs from yourEnd of the insertion Begin of the deletion inEnd of the deletion local Begin of the insertiontimezone, saying: "The dates below are referencing theEnd of the insertion time Begin of the insertionzone ofEnd of the insertion Begin of the deletion inEnd of the deletion the Begin of the insertionmeeting series (TZ of the series), not yourEnd of the insertion Begin of the deletion edit window, thatEnd of the deletion local time Begin of the insertionzone (your currentEnd of the insertion Begin of the deletion should respect summerEnd of the deletion time Begin of the insertionzone).

* Schedule times suchEnd of the insertion Begin of the deletion and show itEnd of the deletion as Begin of the insertion"Every thursday at 9:00AM" is shown inEnd of the insertion Begin of the deletion CEST)and notEnd of the deletion the Begin of the insertiontime zone of the recurring meeting when editing

* Open: Do we allow to "take over" the time zone after creation, moving it to somewhere else? This will result in a lot of rescheduling.End of the insertion Begin of the deletion original CET.End of the deletion


### Screenshots and other files

**Editing this meeting on 22 April 2025 should show the meeting time in CEST, not CET:**

<img class="image_resized op-uc-image op-uc-image_inline" style="width:490px;" src="/api/v3/attachments/470330/content">

**Because now, when I enter submit after selecting 9:00 AM CET, I get 11:00 AM EAT (and 10:00AM CEST)**

**<img class="image_resized op-uc-image op-uc-image_inline" style="width:902px;" src="/api/v3/attachments/470331/content">**

### Environment information

**Community**
**OpenProject 15.5.0**

**Browser:**
Firefox Mac

**Language**
EN