Most platforms treat time as a single global clock. Markets do not work that way. A euro pair at 03:00 UTC and the same pair at 08:00 UTC are, for practical purposes, two different instruments: different spread, different depth, different response to the same size.
What changes across a session
- Spread. Frequently several times wider outside the instrument's primary session.
- Depth. Size that sits comfortably at the London open can move the price materially in a thin Asian session.
- Volatility character. Not merely the level, but whether moves trend or revert.
- Correlation. Relationships often only hold during overlapping sessions.
The consequence for risk limits
A position size that is conservative during the primary session can be aggressive six hours later, without anything about the position changing. A static limit is therefore a limit that is wrong for most of the day — too loose in thin conditions, or too tight in liquid ones.
Two things follow:
- Exposure limits should be aware of the session, or at least set for the thinnest conditions in which a position will be held.
- Holding a position across a session boundary is a decision, and it is usually an unexamined one.
How this shows up in the platform
Session windows are configured per instrument, not globally, and the intelligence layer reports which sessions are open and how current conditions compare with the instrument's typical behaviour for that session.
The simulation on this site models the same thing: instruments are quieter outside their active sessions and most active at the London and New York opens. That is a modelling choice designed to be recognisable, not a claim about any particular day.