So extending Decaf to insert holiday files was not too much of a stretch.
Since we focus on migrating OCS to Exchange, we used the relevant parts of their ICS format for our template.
Create a text file using this template to insert holidays:
SUMMARY:New Year’s Day
LOCATION: Any time zone in your system
DESCRIPTION: No work day
SUMMARY:Holiday on the 14th
DESCRIPTION: Suppose Jan 14 was a holiday in your company
This will insert server-side and happen on the given dates, regardless of time zone (!) So a user in the USA or Canada need only put one holiday file together and can use it for all users.
And you go here to insert it. Our usual restrictions apply. Of course UNDO works for this.
As always, any feedback is welcome.
We're debating whether to include an option to insert for all users on a domain -- which is certainly possible but we're a little leery if it's in demand.