(1) In computing any period of time prescribed by 90-6-301 through 90-6-311, MCA, the day of the act, event, or default after which the designated period of time begins to run is not to be included. The last day of the period so computed is to be included unless it is a Saturday, Sunday or legal holiday, in which event the period runs until the end of the next day which is neither a Saturday, Sunday or a holiday. Whenever a party has the right or is required to do some act or take some proceedings within a prescribed period after the service of a notice or other paper upon him and the notice or paper is served upon him by mail, 3 days will be added to the prescribed period.