(1) Annual leave with wages. Every person employed in a mine who has completed a calendar year' s service therein shall be allowed, during the subsequent calendar year, leave with wages, calculated,-
(a) in the case of a person employed below ground, at the rate of one day for every 2[ fifteen days] of work performed by him, and
(b) in any other case, at the rate of one day for every twenty days of work performed by him.