The |nom_mois filter, when applied to a tag that returns a valid date, will display the common name of the month (January, February...).
Example: for an article published on 22-01-2008,
[(#DATE|nom_mois)] will display "January".
This filter can use the argument "abbr" which will change the resulting display to an abbreviation :
[(#VAL{2015-01-22}|nom_mois{abbr})] will display «jan.»