Time Zones and end of day

Hi, I just need some help working out the correct date and correct archived pivot to load when I am doing backtesting.

On the daily notes archive each pivot can be selected by its date, and my question is what timezone are those dates based on? Are they the timezone of where the instrument is based (say for DAX it would be UTC or UTC+1), or are they all some US timezone like PST?

They are all based on US Eastern Time Zone.