【day off】 —a day away from work, school, etc.:

• The bus-driver spends his “ 【day off】 ” in driving on a pal’s bus, on the box-seat by his pal’s side.

Note: The expression is not equivalent in meaning to the phrase day out—

1. a day away from home when one is free from duty:

• Ollie just loves going to shows and he thoroughly enjoyed his day out.

2. a servant’s free day:

• When it is the maid’s day out, Jack insists on helping with the dishes.

【off day】 —

1. a day when one does not feel fit or does not perform well:

• The bartender could have smiled a little but maybe it was his 【off day】 .

2. = 【day off】 1:

• I could also change which day was my 【off day】 to line up with friends’ birthdays or other celebrations.

Note: The expression does not correlate in meaning with the phrase far- 【off day】 —a day remote in time:

• On that far- 【off day】 I lay on the rocks and listened to the deep rhythm of the Atlantic.