Morgen Timezone Service

This module is used by Morgen desktop and backend services to convert between IANA timezone names and other formats. It relies on data from the following sources:

• moment-timezone (https://github.com/moment/moment-timezone)
• @vvo/tzdb (https://github.com/vvo/tzdb)
• timezones-ical-library (https://github.com/arethetypeswrong/timezones-ical-library)
• tzdata (https://www.npmjs.com/package/tzdata)

Available conversions

IANA to Windows

Required to create events with the EWS API.

const windowsZone = TimezoneService.Timezone.ianaToWindows(ianaZone);

Windows to IANA

Requires when fetching events from EWS or the Graph API, as we always store the zone in the database as a IANA zone.

const ianaZone = new TimezoneService.Timezone(windowsZone).ianaName;

IANA or Windows zone to IANA canonical

This is needed because clients may not be able to handle the full IANA zone names. For example, the mobile app might have a limited number of zones in the local database therefore we want to avoid sending legacy aliases.

const canonicalZone = new TimezoneService.Timezone(ianaZone).ianaName;

Interestingly, both moment-timezone and @vvo/tzdb are unreliable for this opeation For example:

• moment-timezone says Europe/Kiev is canonical, while it should be Europe/Kyiv
• @vvo/tzdb groups names by country and offset, creating spurious links, like Australia/Hobart is linked to Australia/syndey but it should not.

We found that tzdata is the most reliable source for this operation.

IANA or Windows zone to VTIMEZONE

This is needed to generate iCalendar VTIMEZONE components, which in turn is required to generate iCalendar files.

const vtimezone = TimezoneService.Timezone.getVTimeZoneComponent(zone);

How to update

• Update moment-timezone, luxon, tzdata, @vvo/tzdb and timezones-ical-library to the latest versions.
• Update scripts/data/windowsZones.xml with the latest Windows timezone data.
• Run npm run build to update the data files and run the tests.
• Push the changes to the repository.
• Update the commit hash in the package.json of other projects fetching this repo from Github.