T1461: Convert windows timezones into Olson format in iTip
Summary:
iCalendar is used to parse iTip data, but it does not support windows tz.
Fixes T1461
Reviewers: PyKolab Developers, vanmeeuwen
Reviewed By: PyKolab Developers, vanmeeuwen
Subscribers: vanmeeuwen
Maniphest Tasks: T1461
Differential Revision: https://git.kolab.org/D219