What is the test for exceptions to general rule in computing time?

policy concerns, we held that "[b]efore a given case will be deemed to come under an exception to the general rule the intention must be clearly expressed that a different method of computation was provided for." ( Id. at p. 595, 299 P. 713 ; see also In re Rodriguez (1964) 60 Cal.2d 822, 825826, 36 Cal.Rptr. 609, 388 P.2d 881.) Put differently: "Consistent with the need for certainty in the method of computing time, a case will not be found to come under an exception to the general rule unless there is a clear expression of provision for a different method of computation." ( DeLeon v. Bay Area Rapid Transit Dist. (1983) 33 Cal.3d 456, 460461, 189 Cal.Rptr. 181, 658 P.2d 108.)