Hi there,
from history here in the forum, it was planned to include the calendar function in the alfresco explorer and was even available there for some short versioncycles, I heard. It was written that you just needed some files form the old version, which you have to copy into the new version. I never followed up un that one.
With the new version, it was included into share instead, which is a pity, I think. Maybe that helps you a little to dig out the details. Let us all know, if you solved it 🙂 I dont have time in the moment to go hunting myself - sorry.
Norgan