A live overlay of the active session — Asia, London, NY AM — with the time remaining, right on your chart.
The clock shows the active killzone and counts down the time left in it, so you always know where you are in the trading day without leaving the chart.
Most of the day is noise; the killzones are where the moves happen. The clock keeps you patient and ready for the windows that actually pay.
Practice enough sessions with the clock live and you stop checking it — you start to feel where you are in the day on your own.