Quarter centuries index for classical music?

[simbun]

If you can load your collection into Mp3Tag then you can create the tagUpdate script automatically (based on the years in your CURRENT collection) using the export functionality.
Even if you don't use this tagUpdate script as your final solution it'll be useful to see what it looks like, as you were undecided on quarter or half century; the below script will give you both.

Code:

#filename(D:\TagUpdate.txt,utf-8)#loop(%compositionyear%,1)@COMPOSITIONYEAR=%compositionyear%
+COMPOSITIONYEAR_25=#sub(%compositionyear%,#mod(%compositionyear%,25))
+COMPOSITIONYEAR_50=#sub(%compositionyear%,#mod(%compositionyear%,50))
#loopend()

NOTE: I've had to replace $ with # for the code to post to the forum, so just change them back before adding to Mp3Tag.