In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.
Just one little improvement could be made: the time zone "Europe/Frankfurt" does not exist (see https://kodify.net/tradingview/info/syminfo-timezone/). So when you select it, the indicator highlights the zone in UTC. Using "Europe/Berlin" fixes the problem.