Validation action (CCP 860, 863): public agency or interested person must sue within 60 days after the matter comes into existence

[860] A public agency may upon the existence of any matter which under any other law is authorized to be determined pursuant to this chapter, and for 60 days thereafter, bring an action in the superior court of the county in which the principal office of the public agency is located to determine the validity of such matter. ... [863] If no proceedings have been brought by the public agency pursuant to this chapter, any interested person may bring an action within the time and in the court specified by Section 860 to determine the validity of such matter.

CCP 12: "The time in which any act provided by law is to be done is computed by excluding the first day, and including the last, unless the last day is a holiday, and then it is also excluded." CCP 12a: "(a) If the last day for the performance of any act provided or required by law to be performed within a specified period of time is a holiday, then that period is hereby extended to and including the next day that is not a holiday. For purposes of this section, “holiday” means all day on Saturdays, all holidays specified in Section 135 and, to the extent provided in Section 12b, all days that by terms of Section 12b are required to be considered as holidays.(b) This section applies to Sections 659, 659a, and 921, and to all other provisions of law providing or requiring an act to be performed on a particular day or within a specified period of time, whether expressed in this or any other code or statute, ordinance, rule, or regulation." CCP 10: "Holidays within the meaning of this code are every Sunday and any other days that are specified or provided for as judicial holidays in Section 135." Gov. Code 6800: "The time in which any act provided by law is to be done is computed by excluding the first day, and including the last, unless the last day is a holiday, and then it is also excluded." Gov. Code 6804: "“Month” means a calendar month, unless otherwise expressed." Gov. Code 6806: "A day is the period of time between any midnight and the midnight following." CRC 1.10(a): "The time in which any act provided by these rules is to be performed is computed by excluding the first day and including the last, unless the last day is a Saturday, Sunday, or other legal holiday, and then it is also excluded." CRC 1.10(b): "Unless otherwise provided by law, if the last day for the performance of any act that is required by these rules to be performed within a specific period of time falls on a Saturday, Sunday, or other legal holiday, the period is extended to and includes the next day that is not a holiday." Elec. Code 15: "Notwithstanding any other provision of law, if the last day for the performance of any act provided for or required by this code shall be a holiday, as defined in Chapter 7 (commencing with Section 6700) of Division 7 of Title 1 of the Government Code, the act may be performed upon the next business day with the same effect as if it had been performed upon the day appointed.For purposes of this section, the Friday in November immediately after Thanksgiving Day shall be considered a holiday."