LST causes SCHED to assume that all input times are in local sidereal time. If no argument is given, the ``local'' refers to the VLA. Otherwise, a station name can be given to allow scheduling in lst for some other station.
When LST is specified, there are two ways to specify the date. DAY can be used to specify the (modified?) local sidereal day number as found on the VLA monthly schedules. If this is done, YEAR and MONTH are ignored. SCHED senses this situation by testing for a day number larger than the length of a year. The other option is to specify the calendar date in the usual way (YEAR, MONTH, DAY). In this case, SCHED will figure out when on that calendar day the local sidereal time specified for a scan occurs. With this option there is a period of a bit less than 4 minutes each day when the specification is ambiguous (sidereal days are shorter than UT days). If that situation is encountered, SCHED will abort with a request to choose the desired local sidereal day -- the options will be shown.
This parameter was originally indended mainly for VLA-only scheduling. But it is now also used for dynamic scheduling on the VLBA.
When LST is selected, most times are sidereal times or intervals. These include START, STOP, DURation, and DWELL, but not PRESCAN, MINPAUSE, or PRESTART.