N.H. Rev. Stat. Ann. § 623-A:4

Every approved absence shall be for a specified period of time which shall be no longer than necessary to accomplish the purpose of the approved absence. An approved absence shall not exceed 7 days except where necessary for extended medical treatment. An approved absence once begun may be extended by the commissioner of corrections only where necessary to permit accomplishment of the purpose for which the approved absence was originally granted. The commissioner of corrections may shorten or terminate an approved absence in his discretion.