8 hours shall constitute a regular work day for every laborer, mechanic, and apprentice working directly upon the site of the work for any contractor or subcontractor engaged in the performance of the contract. All hours worked on Saturdays, Sundays and all hours worked in excess of 8 hours per day on Monday through Friday and all hours worked on such legal holidays as shall be designated by the Board of Estimates as overtime holidays constitute overtime hours. City Code, 1950, art. 1, §14(a), (b) 1966, art. 1, §16(b),(c) 1976/83, art. 1, §19(a) Ord. 45-225 Ord. 59-1960 Ord. 67-969 Ord. 73-348