Day means calendar day. In computing any period of time prescribed in or allowed by this subpart, the day of the act, event, or default from which the designated period of time begins to run shall not be included. The last day of the period so computed shall be included unless it is a Saturday, Sunday, or Federal legal holiday, in which event the period runs until the end of the next day that is not a Saturday, Sunday, or Federal legal holiday. Intermediate Saturdays, Sundays, and Federal legal holidays shall be excluded from the computation when the period of time prescribed or allowed is seven days or less, not including any additional time allowed for service by mail. If on the day a filing is to be made, weather or other conditions have caused the designated filing location to close, the filing deadline shall be extended to the end of the next day that the filing location is not closed and that is not a Saturday, a Sunday, or a Federal legal holiday. If service is made by mail, three days shall be added to the prescribed period for response.