Spell out months when used alone or with a year as in January or March 2009.
Months are only abbreviated if used with a specific date as in Jan. 2, 2010.
If months are abbreviated, follow these rules; in all cases, be consistent:
Only these months are abbreviated: Jan., Feb., Aug., Sep., Oct., Nov., Dec.
Do not abbreviate these months: March, April, May June, July
Dragoman Style Guide for Figures