Is there a good compelling reason to have the [birthday-calendar] tag? It seems very specific, and could easily fall under [calendars]. Perhaps we should make it a synonym?
This question is what brought this up.
I doubt if birthday-calendar will be used more in the future, if it does we can create a synonym for it (which basically keeps the tag in the system but re-tags it to the other tag). As there is no need to have the tag at all, and it isn't used much (for now), it's best to get rid of the tag and manually re-tag any occurrences to calender instead.
Please note that tags without any questions in will get pruned automatically every 24 hours...