Where a person employed in a mine works on a shift which extends beyond midnight—

(a) for the purposes of sections 28 and 29, a weekly day of rest shall mean in his case a period of twenty-four consecutive hours beginning when his shift ends;

(b) the following day for him shall be deemed to be the period of twenty-four hours beginning when such shift ends, and the hours he has worked after midnight shall be counted in the previous day.