Confused about backtesting different date periods in an EA and DST on MT4

If a server is currently running on EST (GMT - 5)

and the dates I want to backtest is between april 2009 to november 1st

(all within the EDT range)

then should i need to change any manual GMT offset of any EA to

EDT (GMT - 4) for the purpose of the backtest or is the metaquotes data

already timestamped and compensated for this for backtesting.

Is this broker dependent or standard on all servers?

Thanks in advance
Pckeys