The term 'calendar abbr.' refers to abbreviations used for the days of the week and months of the year. The solutions for this crossword are SEPT (4 letters), THURS (5 letters), FEB (3 letters), THUR (4 letters), JAN (3 letters), APR (3 letters), FRI (3 letters), AUG (3 letters), DEC (3 letters), JUL (3 letters), MAR (3 letters), MON (3 letters), NOV (3 letters), OCT (3 letters), SAT (3 letters), SEP (3 letters), SUN (3 letters), THU (3 letters), TUE (3 letters), and TUES (4 letters). These abbreviations are commonly used when writing out dates, such as 'Tues., Jan. 12th'.