Colo. Rev. Stat. § 31-11-103.5
Except as otherwise provided in this article, calendar days shall be used in all computations of time made under the provisions of this article. In computing time for any act to be done before any municipal election, the first day shall be included, and the last or election day shall be excluded. Except when computing business days, Saturdays, Sundays, and legal holidays shall be included, but, if the time for any act to be done or the last day of any period is a Saturday, Sunday, or a legal holiday, the period is extended to include the next day that is not a Saturday, Sunday, or legal holiday. If the time for an act to be done under this article is referred to in business days, the time shall be computed by excluding Saturdays, Sundays, and legal holidays.
C.R.S. § 31-11-103.5