Market hours and the trading day

The hours an instrument can be traded in are not a broker's choice. They are inherited from the venue whose price the contract references, and a contract cannot be quoted honestly when the market underneath it is closed. A share contract follows the exchange the share is listed on. An index or commodity contract follows the futures market it references. A currency pair follows a network of banks that is open continuously from the Asian morning to the New York evening, five days a week.

Because those venues are in different places with different customs, a single account can hold instruments whose trading days start and end at wholly different moments. The schedule is published per instrument, and it is one of the two or three facts about an instrument that changes with the seasons, because daylight saving transitions move some venues relative to others by an hour twice a year.

The boundary between one trading day and the next 

A broker needs a moment at which one accounting day ends and the next begins, and for markets that trade around the clock that moment cannot be inferred from a closure because there is not one. The convention is a stated daily cut off, applied uniformly across the account. Positions still open at that moment are carried into the following day and financed accordingly; positions closed before it settle within the day just ended.

The cut off is a broker level setting expressed in a stated time zone, and it is usually placed at the quietest point in the twenty four hour cycle, after the New York close and before the Asian open. Placing it there minimises the number of positions whose accounting day changes mid movement. It is not midnight in the account holder's own time zone, and expecting it to be is the source of most confusion about which date a trade belongs to.

One consequence is worth stating plainly. A position opened shortly before the cut off and closed shortly after it has been held for minutes and has been carried across a trading day, so it is financed for a night. The financing is a function of the boundary, not of the elapsed time.

Session breaks, and what they suspend 

Many instruments pause for a short period each day even though the venue reopens shortly afterwards. During that pause no price is quoted, which means several things at once: no order can be filled, resting stops and limits cannot trigger even if a theoretical fair price would have crossed them, and any position that is open stays open regardless of what happens elsewhere in the world during the break.

The reopening is where the accumulated information arrives at once, so the first prices after a break are both the most likely to be away from the last ones and the least likely to be backed by depth. That combination, a discontinuous price and a thin book, is why the minutes around a session boundary behave differently from the middle of a session and why fills in them are distributed differently.

Some instruments also have an opening auction rather than a straightforward reopening, in which orders are collected over a period and matched at a single price calculated to trade the largest quantity. Where the underlying venue runs one, the contract's first price of the day is that auction price, and no continuous quoting happens until the auction has concluded.

The weekly boundary 

The longest scheduled closure is the weekend, and it is the one interruption every instrument shares. Continuously quoted markets stop late on Friday in the New York session and resume with the Asian open on Sunday evening, which is a closure of roughly two days. Instruments following a single exchange are closed longer, because their venue also stops for the local evening on Friday and does not reopen until the local morning on Monday.

Positions remain open across it, financing continues to accrue by value date, and no order can trigger while nothing is quoted. The reopening price is set by whatever happened in the interval, which is why the first prices of the week are the most likely of any in it to be discontinuous.

• Open positions persist across every closure. Nothing is closed automatically at the end of a session.
• Resting orders persist unless their time in force expires. A good for day order is cancelled at the venue's end of day, not at a local midnight.
• No stop or limit can be triggered while an instrument is not quoted, however far a related market moves in the interval.
• Financing accrues by value date, so a closure that carries the value date over several calendar days is financed for all of them.

Holidays and shortened sessions 

Venues close for their own national holidays, and a multi market account will therefore have some instruments trading normally while others are unavailable on the same day. Shortened sessions are common around major holidays, where a venue opens as usual and closes several hours early. Both are published in advance by the venue and republished by firms as a holiday schedule, because neither can be inferred from a general calendar.

A holiday in a market that is not itself being traded still matters when it removes the participants who normally quote a related instrument. A currency pair remains quotable when one of its two economies is on holiday, but with a materially thinner book, which shows up as wider spreads and larger effective costs rather than as an outright closure.

Instrument by instrument trading hours, session breaks and the holiday schedule are published in the contract specifications inside the trading platform itself, which for YAL accounts means MetaTrader 5.