Idea for handling timezones

[shironeko]

Hi everyone,

I, like many others on this list, have to move between timezones quite
frequently. As I gathered from the archive, it seems the main complexity in
supporting timezones is the difficulty revolving the change of timestamp format.
So I have an idea, suppose we add a new keyword, "TIMEZONE" that can be set at
the start of the file like so

        #+TIMEZONE: America/Toronto

This specifies the timezone of all timestamps in the file. Together with it,
there can be a function called e.g. org-shift-time, that shifts all the
timestamp in the file to another specified timezone and updates the keyword. Of
course, care needs to be taken when dealing with dates without time, e.g. it
should be treated as at time 00:00 when it is alone or as the start of a time
range, and be treated as at time 24:00 when it is the end of a time range.

Then there could be hooks that offer to run the function automatically when it
detects the user's system or emacs is set to a different timezone as in the file
(e.g. when they open the file, or opens the agenda). This will make sure the
timestamps always aligns with their current one (if they wish).

This change would be backwards compatible, and it should do the job well enough.

Regards,
shironeko