Trading sessions
Trading sessions are the blocks of the 24-hour market day defined by the major financial centers — Sydney, Tokyo, London, and New York — each with its own liquidity, spreads, and behavior.
Forex trades continuously from Monday to Friday because the sessions hand off around the globe. London is typically the deepest market for EUR and GBP pairs, and the London–New York overlap (roughly 8:00–12:00 New York time) concentrates much of the day's volume. The thinnest stretch comes after New York closes, around the 5pm ET rollover, when spreads routinely widen.
Session choice shapes trade character as much as cost. Asian hours are often quieter and range-prone; the London open is known for directional bursts; and each session carries its own cluster of scheduled releases, which is where news trading risk concentrates. A strategy tested on London data is not automatically a strategy for 3am.
Example
Suppose EURUSD trades at a 0.8-pip spread during London hours: entering 1 standard lot costs about $8. The same order placed in the rollover hour at a 3-pip spread costs $30 — nearly four times the toll before price has moved at all. For a scalper taking ten trades, that is the difference between $80 and $300 of pure friction in a day.
In a prop-firm challenge
Evaluations reward routine. Minimum trading days push you to show up repeatedly, and trading the same session each day produces a comparable sample — the only kind a day trading plan can be judged on. Pick the session your setups were built in and that your schedule can actually attend, and avoid the thin hours, where widened spreads and erratic fills make loss limits easier to hit than the chart suggests.