function main()
   while is_run == 1 do
   dt = os.date()
   ddt = string.sub(dt, 10, 14)
   if ddt == "20:45" then is_run = 0
   end
   sleep (1000)
   end
end
 

START_TIME=FixTime(START_TIME)

os.time()<os.time(START_TIME)

START_TIME = "20:00:00"
WORK_DONE = false

   function FixTime(V)
      V=tostring(V)
      local Out = os.date("!*t",os.time())
      local len = string.len(V)
      if len>6 then
         Out.hour,Out.min,Out.sec = string.match(V,"(%d%d)%p(%d%d)%p(%d%d)")
      elseif len==6 then
         Out.hour,Out.min,Out.sec  = string.match(V,"(%d%d)(%d%d)(%d%d)")
      elseif len==5 then
         Out.hour,Out.min,Out.sec  = string.match(V,"(%d)(%d%d)(%d%d)")
      end
      return Out
   end
   
function main()
   START_TIME=FixTime(START_TIME)
   
while true do
   if os.time()<os.time(START_TIME) then
      WORK_DONE=false
   elseif not WORK_DONE then
      message('время работать',1)
      WORK_DONE=true
   end
   sleep(1000)
end
end