Maryland Tax - General Section 1-201
§ 1-201.
  (a)   In this section, "legal holiday" means:
    (1)   the day on which a legal holiday, as defined in Article 1, § 27 of the Code, is observed; or
    (2)   a federal legal holiday.
  (b)   Notwithstanding any other law, when under State or local law, the last day to pay a tax, file a tax return, or perform any other act that relates to taxes under this article falls on a Saturday, Sunday, or legal holiday, performance of the act is considered timely if the act is performed on the next succeeding day that is not a Saturday, Sunday, or legal holiday.
  (c)   For purposes of this section, the last day to perform an act is the last day of any authorized extension of time.