One caution with that approach - if they have customized their standard
calendar rather than customizing a copy of it beyond the company holidays
with hours of work, regional variations, etc, copying your new calendar to
their projects from the Global will lose their changes. Likewise, if they
HAVE made a copy of the original to add additional cusomizations to it, just
copying the newly distributed calendar into the project file won't affect
the calendars they're actually using. Here in Canada we frequently have
that situation because we have multiple base calendars with different
holidays due to jurisdictional issues. The legally mandated holidays in
Ontario are different from those in Quebec, for example, and it's very
common for projects to have resources in both jurisdictions.
If it's just updating company holidays for the coming year, why not simply
distribute a memo and let them update their files by hand? Seems like that
would be a lot less bother both on your end and theirs than sending fresh
files and building the macros to copy them, etc. How much trouble could it
be for them to enter 10-15 holidays by hand as non-working days into the
calendars in their project files when they get the memo? I'm all in favour
of making things as simple as possible for people but there's a limit to how
much hand-holding is really necessary.