Root server should be time zone aware

[jbraswell]

We've punted this for a long time, but now that virtual meetings are a thing and searches are no longer purely geographic, we need to do it. I propose the following.

1. Add a time_zone column next to the current meeting time column. It should be varchar.
2. Valid values for the column should be from https://www.iana.org/time-zones.
3. Only time zone names should be stored in the column. Not the offsets, because the offsets change. It is up to clients to determine the current offset between a source and target time zone when converting.
4. When saving a meeting, automatically calculate the time zone when the time zone has not been manually selected. Otherwise, allow manual selection override.
5. For existing meetings, a data migration is required. Use the google's time zone API to populate the field on upgrade. This is a major upgrade and we should make the UX for updating the meetings really solid. The migration can be punted until a serveradmin both enables the time zone API with the google key and selects a setting in the UI.
6. Expose the time zone field in the semantic API.

This approach should not break anything for existing clients, and should not require anyone to change their actual meeting times.

All that said, virtual-only servers are the only servers at present that need this feature, for example virtual-NA.org. Virtual NA will probably have to fill out the time zone for every meeting manually, because there is no location information to go off of for the time zone. We could probably add the field without a data migration in a first version, but crouton would need to be changed to do time zone calculations when the feature is enabled.

[jbraswell]

First iteration should look like this:

Root server

1. Add column to database.
2. Add drop down to meeting editor.
3. Add field to GetSearchResults
4. Add feature toggle to GetServerInfo

Crouton

1. Check feature toggle in GetServerInfo
2. When feature toggle is on, so time zone conversions

Future iterations can handle the migration path, and this will not impact anyone else - there is no breaking change right now.

[alanb2718]

How do the valid values for the time zone column interact with daylight savings time? For example both EST and EDT are in the time-zones database, so 2) above would say they are both valid values for the column. Unfortunately I'm not seeing a great solution for this. If someone populates the field for a Boston meeting in the summer, they ought to put EDT. Is EDT still used in the winter, and people just have to fix it up mentally? Or use EST even in the summer? That doesn't seem right either.

As an alternative, what if all meetings have a location or pseudo-location? For an in-person or location-centric virtual meeting, what we care about is that it starts at 7pm Boston time, whatever that may be relative to UTC. For a pure virtual meeting, folks could pick a location based on where the organizers are -- or I guess the meeting could live in UTCville, although that may be confusing if there is a daylight savings time change.

[jbraswell]

Human readable time zone names should be stored, not the offset. Client libraries determine the offset, which indeed may change. Example of human readable time zone name is "America/New_York". Storing EST/EDT would be storing an offset. We won't do that.

All popular time zone aware time arithmetic libraries can handle this.

[jbraswell]

Additionally, this offset-agnostic time zone name can be determined automatically for meetings that have location using google's time zone lookup API.

What I am suggesting is essentially the same as what you are suggesting, except I'd like to release a first iteration that requires manual time zone selection to solve a major problem that Virtual NA has. I probably wouldn't officially announce the functionality until it's all super user friendly.

[alanb2718]

OK, that sounds good. So basically my comment boils down to clarifying 2) above to say these should be human-readable time zone names, e.g. "America/New_York".

[pjaudiomv]

<?php
foreach (DateTimeZone::listIdentifiers(DateTimeZone::ALL) as $tz) {
    echo "$tz\n";
}

[jbraswell]

<?php
foreach (DateTimeZone::listIdentifiers(DateTimeZone::ALL) as $tz) {
    echo "$tz\n";
}

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