Meaning of OFF in English
( a. )
Designating a time when one is not strictly attentive to business or affairs, or is absent from his post, and, hence, a time when affairs are not urgent; as, he took an off day for fishing: an off year in politics.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012