In light of an upcoming topic challenge using the tag calendar I wondered if this tag would benefit from being renamed to timekeeping. Calendar might be a more common word, but it rather arbitrarily excludes some topics that would be covered by a timekeeping tag1.
I'd suggest renaming calendar to timekeeping, since there seems to be no point in having two tags coexist when one is included by the other but the extra ground isn't massive. Perhaps calendar should be made a synonym of timekeeping though.
1: such as a hypothetical "How long would this society's seconds be?" question