Ok, I'm
not the best person to respond, particularly as I have not dabbled in templates and don't otherwise see the need for them. It could be my own ignorance though.
Anyway... That seems like an awful lot of work to produce 'useless' intermediary data. I say 'useless' because if the year, month and day columns are not otherwise needed, you're storing data unnecessarily.
I've just found out about subgroups and think they might be of use in this instance:
http://manual.calibre-ebook.com/sub_groups.html
You might be able to create a single custom column with a data format of:
YYYY.MM.DD.Q, making use of numbers with leading zeros for all segments except the last. The format is pretty much standard date field notation, adding a "Quarter #" into the mix. The only thing that would be odd is the quarterly / seasonal releases will be slightly out of true placement among other data - because day "00" is going to appear at the beginning of any listings for the month.
You could also do a
YYYY.DDD format where days are # of days in the year (ex: Dec 25, 2012 = 2012.359). While accurate, this latter format is not as readable / user friendly.
Using subgroups might have the added benefit that you could output / display all of the publications in your database released in Oct 1953, for instance. Searching on #custom_column_name:"1953.10".
I'm not sure if these ideas are what you need, but I hope I've helped. (Or at least prompted someone else to jump in and offer a more viable suggestion!)