I downloaded history into MT4's History Center on two servers - one in UTC (Alpari) and another in ET(Gain). Both had UTC timestamps.
Your server hosts were kind enough to enforce UTC timestamping.
But to write a Zorro plugin that accounts for all servers (including the one in my screenshot, look closely...), it must enforce an offset based on time difference between reported server time and UTC.
MT4/MT5 is a sort of Plato's Cave, if you will.
