In computing any period of time prescribed or allowed by this part, by notice, order or regulation or by any applicable statute, 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 for the Department, in which event the period runs until the end of the next day that is neither a Saturday, Sunday, nor holiday. When the period of time prescribed is seven (7) days or fewer, intermediate Saturdays, Sundays, and holidays shall be excluded in the computation, unless otherwise specified by the DOT decisionmaker or the administrative law judge assigned to the proceeding, as the case may be.