I don't have a specific answer but have seen similar things in other database driven applications.
The data should be stored in the database against UTC. The user locale defines at what time the data is displayed. Issues can arise when different users are located in different locales and are accessing the same information.
Imagine if you were creating a meeting invitation in Fairfax (currently UTC-4) for 0900h and invite a user from a Paris office (currently UTC+2). They will see this as 1500h. Now if you put in an out of office entry for 28 July, think about when this starts and stops for someone viewing this from another timezone and more importantly, how does the software handle and present this?
For meetings, this is easy - just accept the original entry. For OoO it's tricky and the software may simplify things, perhaps based on stored start of day for the locale and that can shift either side of midnight foranother locale.
Perhaps the Alfresco devs could enlighten.
Cheers, Sasquatch