Unless otherwise provided, reference to "days" in this subchapter shall mean calendar days. For purposes of determining timeliness of filing and receipt of documents transmitted by mail, 3 days shall be presumed added to the prescribed period. If the last day for filing a document is a Saturday, Sunday, legal holiday or a day on which the Bureau's offices are closed, the time for filing shall be extended to the next business day. Transmittal by mail shall mean by first-class mail.
34 Pa. Code § 125.156