Answer:

mon

Answer	Crossword Clue
MON	Calendar column: Abbr.
MON	Sun follower?
MON	Many a fed. holiday

MON	Most common day to call in sick: Abbr.
MON	Part of many a three-day weekend: Abbr.
MON	Fellow in Jamaica
MON	Kingston bro
MON	The day of M.L.K. Day: Abbr.
MON	Kingston dude
MON	When Presidents' Day is always celebrated: Abbr.
MON	Datebook abbr.

MON	Sun. follower
MON	Tues. preceder
MON	Jamaican fellow
MON	Many a federal holiday: Abbr.
MON	Calendar abbr.
MON	Back-to-sch. time
MON	Jamaican term of address
MON	Tue. preceder

MON	Back-to-work time: Abbr.
MON	Back-to-school time: Abbr.
MON	French possessive
MON	... cheri
MON	... ami
MON	Time to get back to work: Abbr.
MON	Fall football night: Abbr.
MON	Oct. start of a new Supreme Court session

MON	Dieu et ... droit (motto of England)
MON	Guy in Jamaica
MON	Many a legal holiday: Abbr.
MON	One reggae fan to another
MON	Day of the week: Abbr.
MON	...ami