Allow a code for localised time

[Biep]

Often room members want to agree on a time (to chat, or meet up otherwise), yet with all the different time zones it is a lot of calculating to find out what the proposals mean. If messages would accept a code such as ${time:15:30}, which would be interpreted as a universal time corresponding to the local 15:30 of the sending session, and would be translated into the local date/time of the receiving session, such things would be a lot easier.
Obviously, this scheme allows future extensions for other relative data.

[Biep]

Also exceedingly useful for referring back to old messages: In her message of ${time:15:30}, @someone:matrix.org suggested the opposite.
For the sake of privacy, it should be translated into something that doesn't refer to the sender's time zone.
The server doesn't have to know about this, and clients could use the code internally too - as when replying or quoting.