I just read:
In a well-designed language, the Day-of-Week names would be of equal length and in alphabetical order, starting with Monday (but giving other days an additional earlier name for use in locations where the week starts too soon). They would start with different three-, two-, and one-letter abbreviations.
The month names would be also be of equal length and in alphabetical order, with distinct abbreviations.
A cute idea. Perhaps I should implement that in a conlang/conworld some day.