git-annex/doc/bugs/Windows_file_timestamp_timezone_madness.mdwn

Windows has an unfortunate handling of time zones, which means that when
the time zone is changed (or DST changes), the timestamps of files also
appear to change.

This means that after such a change, git-annex will see new mtimes, and
want to re-checksum every file in the repo.

[[!tag confirmed]]

> Update: Actually, I seem to have been getting confused by behavior of
> cygwin terminal setting TZ. That indeed led to timestamp changes when the
> time zone changed. I have made git-annex unset TZ to avoid this.
> 
> Without TZ set, time stamps are actually stable across time zone changes.
> Ie, a simple program to read the time stamp of a file and print it
> always shows the same thing, before and after a timezone change.
> 
> However, and here's where it gets truely ghastly: A program that stats a
> file in a loop will see its timestamp change when the timezone changes.
> I suspect this might be a bug in the Haskell RTS caching something it
> should not. Stopping and re-running the program gets back to the
> original timestamp.
>
> I have not tested DST changes, but it's hard to imagine it being any
> worse than the above behavior.
> 
> So, that's insane then. We can't trust timestamps to be stable on windows 
> when git-annex is running for a long period of time. --[[Joey]]
> 
> > [[fixed|done]], using the inode sentinal file to detect when windows
> > has lost its mind, and calculating its delta from insanity. --[[Joey]]