study("Session bars", overlay=true)
t=time(period,"1430-2100")
t0=time(period, "0100-0101")
t1=time(period, "0900-0901")
bgcolor(color = na ( t0 ) ? na:blue, transp=60)
bgcolor(color = na ( t1 ) ? na:blue, transp=60)
bgcolor(color = na ( t ) ? red:green, transp=70)