This Act was passed by King James I after Guy Fawkes' failure to blow up the King, the Lords and the Commons at the Opening of Parliament. For two centuries afterwards, special church services were held to commemorate his failure, under the provisions of the Act.
An Act for a Public Thanksgiving to Almighty God every Year on the Fifth Day of November. [Thanksgiving Act]
Parliamentary Archives, HL/PO/PU/1/1605/3J1n1