Unfortunately it is. Because the S3 and T3 auto traders use studies from multiple charts, and they depend on session times and events based on New York time, all your trading charts need to be on New York time. This is a limitation of Sierra Chart, recently confirmed to be something they don’t plan on changing. Therefore, you will get inaccurate levels, and overlays unless you globally change Sierra to trade in New York Time. This setting is in Global Settings>> Data/Trade Service Settings.
Custom Studies for Sierra Chart