4.2 KiB
MSC4175: Profile field for user time zone
Knowing another user's time zone is useful for knowing whether they are likely to respond or not. Example uses include:
- Showing a user's time zone or time zone offset directly.
- Showing a user's local time (with hints of whether it is day or night there).
Proposal
Profiles can provide an optional m.tz field with values equal to names from the
IANA Time Zone Database.
Clients can set and fetch this via the normal API endpoints.
- Servers MAY validate that the value is a valid IANA time zone. If deemed invalid
they MUST return a 400 error with error code
M_INVALID_PARAM. - Clients MUST handle invalid or unknown values.
If the field is not provided it SHOULD be interpreted as having no time zone information for that user.
Potential issues
Clients may need to understand IANA time zone names to show useful information to users.
Some languages make this easy, e.g. JavaScript can handle this using
Date.toLocaleString().
This may cause clients to bundle the IANA time zone database (and thus also keep it
up to date).
Clients will need to manually update the profile field when the user changes time zone. This could be automated by clients based on location, or left as a manual change to users.
Clients may wish to periodically fetch the time one of other users as it is liable to change somewhat frequently. Currently, profile data isn't propagated/synchronized between servers, but that's left to a future MSC to solve. It is recommended that clients cache the value for 12 - 24 hours.
Alternatives
The time zone offset could be included directly (in minutes/seconds or in [+-]HH:MM form).
This would require clients to manually update the profile field during daylight
savings. Using the IANA time zone name is robust against this.
RFC7095: jCard The JSON Format for vCard format could be used instead, but this doesn't make much sense unless the entire profile was replaced.
RFC9553 offers an alternative
representation for contacts (which is not backwards compatible with vCard). There
exists timeZone field under the addresses field which uses an time zone name
from the IANA Time Zone Database.
Note there's an alternative jCard format which is a non-standard derivative of hCard.
Competitive analysis
Slack's users.info API call includes
3 separate fields:
tz: the time zone database name (e.g."America/New_York")tz_label: a friendly name (e.g."Eastern Daylight Time")tz_offset: offset in seconds as an integer (e.g.-14400)
XMPP uses either:
- XEP-054 uses vCard (RFC2426) converted to XML via draft-dawson-vcard-xml-dtd-01
- XEP-0292 uses xCard: vCard XML Representation (RFC6351), see also vCard4 (RFC6351)
Rocket.Chat provides a user's time zone offset
in the utcOffset field.
Mattermost returns an object with the user's manual and/or automatic IANA time zone name.
Discord, Twitter, and IRC don't provide a user's time zone.
Security considerations
Showing a user's time zone gives some information to their location. There is currently no way to limit what profile fields other users can see.
Clients may wish to warn users when providing a timezone and give the option to not include it in their profile.
Unstable prefix
us.cloke.msc4175.tz should be used in place of m.tz.
Dependencies
Requires MSC4133.