Sessions in schedule block overlap when viewing from certain locations/timezones

[jorgeatorres]

Describe the bug

This might be related to #559. When visiting our WC site from certain locations (for instance, London (UK) or Barcelona (Spain)), some sessions start to overlap making the whole thing unreadable.
These sessions seem to be the ones that fall near the time the day changes (in that timezone), but I'm not sure if that's the real reason.

It is worth mentioning that to work around #559, our site's timezone was changed to UTC (from the previously set "America / Bogota" or UTC-5). I can confirm that the sessions look fine when in UTC-5 or UTC-3, so maybe the the problem only affects UTC+something timezones?

Is there a something we can do from our side besides manually creating a schedule page (not using the block)? Thanks!

To reproduce

Steps to reproduce the behavior:

1. Set time zone to "Bogotá - Colombia" or "Buenos Aires - Argentina".
   On macOS: Go to System Preferences > Date & Time > Time Zone.
2. Go to https://colombia.wordcamp.org/2020/agenda/.
3. Confirm that the whole schedule looks fine.
4. Change time zone to "London - United Kingdom" (British Summer Time) or "Barcelona - Spain" (Central European Summer Time).
5. Go to https://colombia.wordcamp.org/2020/agenda/.
6. See how some session items look wrong, either overlapping or times being displayed over borders. See screenshots below for examples.

Expected behavior

Schedule should look correct in all timezones.

Screenshots

WordCamp

https://2020.colombia.wordcamp.org/

System (please complete the following information):

• Device: Laptop
• OS: macOS 10.15.6
• Browser: Chrome
• Version: 84.0.4147.135

[iandunn]

Note to self: another way to test the time zone is with TZ="Europe/London" open /Applications/FirefoxDeveloperEdition.app in terminal, and verify with Intl.DateTimeFormat().resolvedOptions().timeZone and wp.date.format('P') in browser console. That might avoid unintended side-effects from changing the OS timezone.

[iandunn]

Is there a something we can do from our side besides manually creating a schedule page (not using the block)?

I'm hoping to have this fixed soon, but in the mean time you can switch to the block's Single Column Layout style.

[iandunn]

@jorgeatorres, it looks like we might need to wait for WordPress/gutenberg#25078 and WordPress/gutenberg#22193 to be fixed & released before we can fix this.

The next Gutenberg released isn't scheduled until after Colombia is over, so I'd recommend switching to the Single Column Layout block style in the meantime. That should prevent the overlap problem.

[iandunn]

It looks like the above 2 PRs will solve this, but only when using string timezones 😆 🤷🏻 .

Keeping open until we upgrade to v9 (or possibly later if WordPress/gutenberg#25083 is in a later version).