VMS Help V73 Features, System Management Features, Daylight Savings Time  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    System parameter AUTO_DLIGHT_SAV controls whether OpenVMS
    will automatically change system time to and from Daylight
    Savings Time when appropriate. A value of 1 tells OpenVMS to
    automatically make the change. The default is 0 (off). This is a
    static parameter.

    However, if you have a time service (such as DTSS), that time
    service continues to control time changes, and OpenVMS does not
    interfere. Do not enable automatic daylight savings time if you
    have another time service.

    For more information, refer to the OpenVMS System Manager's
    Manual.