Timezone Handling Issue in translate.wordpress.org Event System

[vgnavada]

Summary:
@amieiro identified an issue with how the event system handles time zones when he was helping us to create an event in translate.wordpress.org, particularly in relation to Daylight Saving Time (e.g., CET to CEST) and cross-timezone scheduling.

Issue Description:
The bug arises when scheduling an event from a location currently in CET that will switch to CEST by the event date. The event creator had to manually adjust the timing to align with Asia/Kolkata timezone due to a 3.5-hour difference. The system did not account for this shift automatically.

Expected Behavior:
The event system should:

• Correctly handle future timezone transitions (like CET to CEST).
• Automatically convert event times based on both the creator's and participants' time zones.
• Accurately reflect Daylight Saving Time changes.

Actual Behavior:
Times were not properly adjusted for the CEST shift, resulting in manual corrections being necessary to ensure the correct time was shown for Asia/Kolkata participants.

Example Correction Made:

• Start: Saturday, 5 April 2025 at 13:30 CEST → 17:00 IST (Asia/Kolkata)
• End: Sunday, 6 April 2025 at 20:19 CEST → 23:49 IST

Steps to Reproduce:

1. While in CET, schedule an event for April (when CEST is active).
2. Compare the event time displayed for Asia/Kolkata.
3. Notice the incorrect conversion due to unhandled DST shift.

Suggested Fix:

• Ensure timezone and DST changes are applied based on the event date.
• Offer a clear preview of how times appear across different time zones.