Time Zone Issue in Edit Phase Dialog: Start Time and End Time Cannot be Saved Correctly

Description

In the "Edit Phase" dialog, the Start Time and End Time fields do not account for time zones and default to UTC. As a result, when I set the End Time to "31 Mar 12:00 AM" in my local time, it is displayed incorrectly upon loading the page. Specifically, the time shows as "30 Mar 4:00 PM." After saving, I receive a "Phase Errors" message. When reopening the dialog, the End Time is displayed as "30 Mar 8:00 AM."

Steps to Reproduce

• Set timezone to UTC.
• Open the "Edit Phase" dialog.
• Set the End Time to "31 Mar 12:00 AM" in the local time.
• Save.
• Set timezone to UTC+8.
• Load the page again.
• Observe that the End Time changes to "30 Mar 4:00 PM". (Screenshot 1)
• Save.
• A "Phase Errors" message appears. (Screenshot 2)
• Reopen the "Edit Phase" dialog and notice that the End Time is now "30 Mar 8:00 AM". (Screenshot 3)

If you're having trouble understanding, please watch the video below, rather than closing the issue and stating that this is not a bug.

https://github.com/user-attachments/assets/ba166004-dbc7-4a90-ad3c-0e8a9795e593

Screenshots

No files or tests are named. Start by locating the Edit Phase dialog and the code that reads and writes Start Time and End Time, then reproduce the UTC and UTC+8 sequence; done means saved times remain consistent when the dialog is reopened and no Phase Errors message appears.