The Convert Date String to Quadword routine converts an absolute
    date string into an OpenVMS internal format date-time quadword.
    That is, given an input date/time string of a specified format,
    LIB$CONVERT_DATE_STRING converts this string to an OpenVMS
    internal format time.

    Format

      LIB$CONVERT_DATE_STRING  date-string ,date-time

                               [,user-context] [,flags] [,defaults]

                               [,defaulted-fields]