When calling date with format character "M", the three-letter abbreviation is returned; however, when one wants to place a period after this three letter abbreviation, there is trouble in May...

For example:
date("M.", $january_date) ====> Jan.
date("M.", $february_date) ===> Feb.
date("M.", $may_date) ========> May. (not an abbreviation!)

I know all of this can be fixed with a few lines of code that checks to see if the month is May before adding the period, but it seems to me that an "abbreviated three-letter textual month" format character could be valuable.

But, then the subject of AP-style abbreviations comes up... Their the list of months and abbreviations (or lack-thereof) reads:
Jan., Feb., March, April, May, June, July, Aug., Sept., Oct., Nov., Dec.