by day
During the day.
He is a policeman by day and a thief by night.
Those who dream by day are cognizant of many things that escape those who dream only at night. Edgar Allan Poe
For age is opportunity no less Than youth itself, though in another dress, And as the evening twilight fades away The sky is filled with stars, invisible by day. Henry Wadsworth Longfellow
Now Autumn's fire burns slowly along the woods And day by day the dead leaves fall and melt. William Allingham
He who does not lose his way by night will not lose his way by day. Nigerian Proverb
By day they're ready to divorce, by night they're ready for bed. Yiddish Proverb
God deliver us from a gentleman by day and a friar by night. Spanish Proverb