Server time versus local time and the bugs they cause

[Amanhasnoname]

Charts run on the broker's server time, not the clock on your wall. That sounds trivial until a strategy that filters sessions by hour starts behaving oddly twice a year.

Most brokers use GMT+2 or GMT+3, shifting with US daylight saving so that the daily candle closes at 5pm New York. But the US and Europe change their clocks on different weekends, so for a couple of weeks each year the offset between server time and London time is different from the rest of the year.

Anything built on fixed hours, like avoiding the first 15 minutes of the London open, will quietly shift by an hour during those weeks. The strategy might take trades during a window it was designed to avoid.

The fix is to anchor rules to a real time zone, usually New York or London, and convert, rather than hardcoding server hours. Another option is to check the calendar for those mismatch weeks and trade smaller.

Has a time-zone shift ever shown up in your results without you noticing at first?