A day on which work is performed, as distinguished from Sunday, festivals, etc., a working day.

the culturally established number of hours that a person ideally spends at work each day.

a day on which work is done

the amount of time that a worker must work for an agreed daily wage; "they work an 8-hour day"

a day on which most people do a job for money, or the amount of time each day a person spends doing their job

A calendar day that the Contractor normally works.