What a trading session is, and why it matters
A trading session is the window during which a financial centre is open and its participants are at their desks. The market may run around the clock; the people who trade it do not.
Currency and futures markets are almost continuous, but activity is not. That mismatch is what creates sessions: the market is open everywhere, the volume is concentrated somewhere.
The consequence is direct and checkable on your own chart. The volume of a ten in the morning candle has nothing in common with a three in the morning one. And volume is what decides the cost of an execution, as the lesson on large orders explains.
A level taken out with people on the other side and the same level taken out into a vacuum do not tell the same story, and no indicator will tell you which one you are looking at. The clock will.
⚠️ This is the only element in the whole corpus that is objective data rather than a reading. An hour cannot be reinterpreted after the fact, which is what makes it testable where the rest is not.
The three sessions, in London time
The Asian session runs roughly from midnight to eight in the morning. It is quiet on European pairs, livelier on the yen and the Australian dollar, and it is often where the narrow range forms that the rest of the day will break.
The London session runs from about eight to five. It is the heaviest in foreign exchange, and it is the one that most often gives the day its range.
The New York session runs from half past one to nine in the evening. The window that genuinely matters is the overlap with London, half past one to five: two centres open at once, so twice as many people on the other side.
None of this is read in the abstract, it is read against the instrument. A US index has no reason to live by the rhythm of an Asian pair, and the internal calendar of a futures contract depends on the exchange that lists it.
Check these windows yourself rather than copying them: daylight saving shifts them by sixty minutes twice a year, and not on the same dates on both sides of the Atlantic.
Killzones, and what they claim to add
The ICT vocabulary cuts these sessions into narrower windows it calls killzones, usually one to three hours around an open. The idea is that most of a day's movement is decided inside those windows.
The claim is a strong one, and it has the merit of being checkable with no argument possible. All it takes is recording, across a hundred sessions, the hour at which the high and the low of the day printed.
That is a spreadsheet, two columns, one evening of work. The result is a histogram of hours, and it is the same for everyone: not an opinion, a count.
What you will probably find is a real concentration, less spectacular than promised, and above all different from one instrument to the next. That is the kind of result that does not sell well on video, and it is the one that serves you.
⚠️ A window that concentrates the extremes does not tell you which way to enter. It tells you when it is worth looking, which is information about time, not about direction.
What the hour genuinely changes
Three things change with the hour, and all three can be measured on your own account, which is rare in this field.
The spread first. It widens when few people are around and tightens when the main session opens. On a small account that spread is a large share of the real cost of a round trip.
Range second. The same breakout strategy does not produce the same number of usable signals depending on the window, and a stop calibrated on London is often too wide for the Asian session.
Follow-through third. A break during a busy session has the volume to go somewhere; the same break in a quiet hour usually runs out of participants.
People search for the best hour to trade as if it were one question. It is three, and the useful way to ask it is: at what hour does my cost fall, and at what hour do my signals follow through?
The timing mistake that costs the most
It does not come from the theory, it comes from the time zone. An hour quoted in an American video is New York time, an hour quoted on a British forum is London time, and your chart is probably displaying something else again.
Set your chart once and for all to a zone you understand, and write that zone next to your records. Without it, thirty sessions of history become unusable the moment the clocks change.
The second mistake is reasoning in fixed hours when the market reasons in opens. The gap between Europe and the United States is not constant across the year, and for two weeks a year it is one hour smaller.
The third is running the same strategy across every session with the same settings. A stop that suits London is often too tight in New York and too wide in Asia, and the trader concludes the method has decayed when what changed was the clock.
⚠️ Record the hour of every trade in your trading journal. It is the easiest column to fill and one of the most revealing: plenty of people discover their entire annual loss sits inside two hours of the day.
Practising: a hundred sessions, two columns
Pick one instrument and one time zone, and write them down. Then record, across a hundred sessions, the hour of the high and the hour of the low of the day. Two columns, a hundred rows.
Count how many fall into each hourly window. You get a histogram, and that histogram is the only serious answer to whether killzones exist on YOUR market.
Add a third column if you want to go further: the range of the session. You will then see whether the days when the extreme falls inside the stated window are also the days that move, which is not automatic at all.
Repeat on a second instrument. The comparison between the two will teach you more than the first hundred rows, because it tells you whether you found a property of the market or a property of your sample.
This record is worth keeping and rereading. It is one of the few pieces of work in this course whose result does not go stale from one season to the next, provided you redo it once a year.
Key takeaways
- The market runs almost continuously, but the people trading it do not work at night. That mismatch is what creates sessions.
- The hour is the only objective datum in this whole corpus: it cannot be reinterpreted afterwards, so it can genuinely be tested.
- Three sessions matter, Asia, London, New York. The densest window is the London and New York overlap.
- Killzones can be checked in one evening: record the hour of the high and the low across a hundred sessions, and count.
- A window that concentrates the extremes says WHEN to look, never which way to enter.
- The most expensive mistake is the time zone, not the theory. Write your zone next to your records or they become unusable.
Going further
These blog articles dig into this lesson's ideas, one subject per article.