Answer:

sep

Answer	Crossword Clue
SEP	Back to school mo., usually
SEP	Calendar abbr.
SEP	9, on the cal.

SEP	Unconnected: Abbr.
SEP	After Aug.
SEP	Mo.
SEP	Mo. in summer
SEP	Ninth mo.
SEP	Autumn mo.
SEP	Start to fall? (abbr.)
SEP	Mo. in which Australia observes Father's Day

SEP	30-day mo.
SEP	Back-to-school mo.
SEP	Equinox mo.
SEP	LCD watch month
SEP	When the regular NFL season begins
SEP	Labor Day mo.
SEP	Virgo's mo., maybe
SEP	Father's Day mo. in Australia

SEP	Mo. when asters usually flower
SEP	9, in many cases: Abbr.
SEP	Fall mo.
SEP	Ninth in a series: Abbr.
SEP	9th mo.
SEP	Mo. to "fall back" on?
SEP	IRA for small companies
SEP	Autumnal equinox mo.

SEP	End-of-summer mo.
SEP	When the regular NFL season opens
SEP	Cal. abbr.
SEP	National Chicken Mo.
SEP	Elephant Appreciation Day mo.
SEP	It comes between Aug. and Oct.
SEP	Pennant race mo.
SEP	Talk Like a Pirate Day mo.

SEP	When sch. often starts
SEP	Libra's mo., perhaps
SEP	Michaelmas mo.
SEP	NFL season opening mo.
SEP	National Preparedness Mo.