Labor Code of the Philippines -BOOK THREE CONDITI..

Chapter II
WEEKLY REST PERIODS

Art. 91. Right to weekly rest day.
It shall be the duty of every employer, whether operating for profit or not, to provide each of his employees a rest period of not less than twenty-four (24) consecutive hours after every six (6) consecutive normal work days.

The employer shall determine and schedule the weekly rest day of his employees subject to collective bargaining agreement and to such rules and regulations as the Secretary of Labor and Employment may provide. However, the employer shall respect the preference of employees as to their weekly rest day when such preference is based on religious grounds.

Art. 92. When employer may require work on a rest day. The employer may require his employees to work on any day:
In case of actual or impending emergencies caused by serious accident, fire, flood, typhoon, earthquake, epidemic or other disaster or calamity to prevent loss of life and property, or imminent danger to public safety;

In cases of urgent work to be performed on the machinery, equipment, or installation, to avoid serious loss which the employer would otherwise suffer;

In the event of abnormal pressure of work due to special circumstances, where the employer cannot ordinarily be expected to resort to other measures;

To prevent loss or damage to perishable goods;

Where the nature of the work requires continuous operations and the stoppage of work may result in irreparable injury or loss to the employer; and

Under other circumstances analogous or similar to the foregoing as determined by the Secretary of Labor and Employment.

SOURCE:
http://www.dole.gov.ph/labor_codes.php?id=39