First, ProScreener has a 254-bar lookback limit, so I don’t think it’s possible to gack to that date (maybe it could, considering no trading days).
Second, the only past/future date referencing instruction is DateToBarindex() (https://www.prorealcode.com/documentation/datetobarindex/), but it can only be used in graphical instructions.
So you should use only PERIODS to access past bars.