The crossword solutions for the term DATEBOOK ABBR. are MAR (3 letters), THURS (5 letters), DEC (3 letters), FRI (3 letters), MON (3 letters), OCT (3 letters), THU (3 letters), TUE (3 letters), and APPT (4 letters). These abbreviations are commonly used in datebooks to represent days of the week and months of the year. MAR stands for March, THURS stands for Thursday, DEC stands for December, FRI stands for Friday, MON stands for Monday, OCT stands for October, THU stands for Thursday, TUE stands for Tuesday, and APPT stands for appointment.