Appointment availability intervals are generate in browser time zone and not calendar time zone

Steps to reproduce

1. Change calendar to a different time zone then the browser time zone (Calendar: Europe/Berlin, Browser: America/Toronto)
2. Create new appointment schedule (Mon to Fri, 9am to 5pm)
3. Check appointment slots for schedule (use link)

Expected behavior

Appointment availability intervals should be created with calendar time zone

Actual behaviour

Appointment availability intervals are created with the browsers time zone

Calendar app version

Main

Test Results

Appointment availability Intervals created with:

Calendar set to Europe/Berlin
Browser set to America/Toronto
Time set to 9am to 5pm

{
    "timezoneId": "Europe\/Berlin",
    "slots": {
        "MO": [
            {
                "start": 1732543200,
                "end": 1732572000
            }
        ],
        "TU": [
            {
                "start": 1732543200,
                "end": 1732572000
            }
        ],
        "WE": [
            {
                "start": 1732543200,
                "end": 1732572000
            }
        ],
        "TH": [
            {
                "start": 1732543200,
                "end": 1732572000
            }
        ],
        "FR": [
            {
                "start": 1732543200,
                "end": 1732572000
            }
        ],
        "SA": [],
        "SU": []
    }
}

Epoch conversion for Monday start in Europe/Berlin

1732543200 converts to Monday November 25, 2024 15:00:00 (pm) in time zone Europe/Berlin (CET)

Epoch conversion for Monday start in America/Toronto

1732543200 converts to Monday November 25, 2024 09:00:00 (am) in time zone America/Toronto (EST)

Issue

Appointment availability intervals are created with the browsers time zone and not the calendars.

A secondary issue is that epoch is a static number of seconds from a specific start point and defines a different time for every time zone. Epoch time will also differ during Standard and Daylight Savings time.

Solution

Use seconds from start of day for availability intervals