VLIB_AM_PM [
  ( a m 
    ?VSUB_IN_THE_MORNING
  ) {return("A.M.")}
  ( p m 
    ?VSUB_AT_NIGHT
  ) {return("P.M.")}
  VSUB_IN_THE_MORNING {return("A.M.")}
  VSUB_AT_NIGHT {return("P.M.")}
  noon {return("P.M.")}
  midnight {return("A.M.")}
]

VSUB_IN_THE_MORNING [
  ( in the morning ) 
  ( this morning )
]

VSUB_AT_NIGHT [
  ( at night ) 
  tonight
  ( [ ( in the ) this ] [ afternoon evening ] )
]