Rule 131
Calculation of periods

(1) Periods shall be laid down in terms of full years, months, weeks or days. 

(2)¹⁵⁹ Computation shall start on the day following the day on which the relevant event occurred, the event being either a procedural step or the expiry of another period. Where the procedural step is a notification, the relevant event shall be the deemed receipt of the document notified, unless otherwise provided.

(3) When a period is expressed as one year or a certain number of years, it shall expire in the relevant subsequent year in the month having the same name and on the day having the same number as the month and the day on which the said event occurred; if the relevant subsequent month has no day with the same number, the period shall expire on the last day of that month. 

(4) When a period is expressed as one month or a certain number of months, it shall expire in the relevant subsequent month on the day which has the same number as the day on which the said event occurred; if the relevant subsequent month has no day with the same number, the period shall expire on the last day of that month. 

(5) When a period is expressed as one week or a certain number of weeks, it shall expire in the relevant subsequent week on the day having the same name as the day on which the said event occurred.