Expiration types determine how long an order will stay open without filling. Your order type is very important for limit orders, but understanding them can also remove a lot of confusion for market orders.
There are many different order types, but we can focus just on a few of them to get a feel for how they work. You may have more or less depending on your brokerage.
Good Till Day
Day, or Good-til-Day, orders will expire at the end of the trading day when the markets close (In the US, it is 4:00 pm ET). If the conditions for your order to fill are not met at the end of the trading day, the order will expire. Market orders are placed as “Good Till Day” by default, with the only condition being that there is sufficient volume in the actual markets for the trade to go through.
Some brokerages allow partial-order filling for market orders, which means that your order will fill to what the volume allows until the market closes, then the remaining part of the order is cancelled at the end of the day.
If a Good Till Day order is placed after hours, it will expire at the end of the next trading day (unless it executes).
Cancel, or Good-til-Cancelled (GTC), orders will expire only when you go and manually cancel the order. These orders never expire, meaning they are often popular for stop-loss orders or other very long-term trading strategies.
Date, or Good-til-Date, orders will expire at the date you set, at the end of that trading day when the markets close (In the US, it is 4:00 pm ET). This allows you to keep an order for longer than a day, but you don’t necessarily want it to sit open forever.
An example of this is when you know a company you hold is releasing an earnings report; if the earnings are bad the price starts to really go down, you want to sell it quickly, but if the price doesn’t drop then you would prefer to hold on to it. You could set your stop-loss order to expire the day after the earnings release, which would protect against losses up until that date.
More Complex Order Types
These are more complex orders; you probably will not encounter them with normal brokerage accounts (although some are becoming slightly more common). These are most often used by institutional traders, or professional traders.
Extended can mean different things depending on who is offering it; usually they are for pre- and after-market trading (for example, stay open until after the after-market trading period on this date)
Fill or Kill
This is a shorter version of “Good Till Day”, this order only stays open for a few minutes. If there is not sufficient volume in the markets to execute, it will cancel.
Immediate or Cancel
This works the same as “Fill or Kill”, except partial order fulfillment is allowed. You will buy up as much of your order as the market will sell you within a few minute (or second) window, and whatever is left is cancelled.