The day a transaction is agreed — T, from which everything else is counted.
The trade date is when the parties agree a transaction. It is the reference point the settlement cycle counts from, which is why cycles are written T+1 and T+2.
It is not when anything moves. On the trade date the obligation exists and nothing has been delivered, which is the exposure clearing arrangements are designed to manage.
Trade date is also determined by the market's own calendar and hours: a transaction agreed after a market's close may carry the following trading day's date, so the same instant produces different trade dates in different venues.
Trade date is agreement; settlement date is completion. The interval between them is the settlement cycle.
See also settlement date · settlement cycle · trading day · settlement finality
We hold no settlement or clearing calendars. This entry defines the term and demonstrates nothing, because a near-miss borrowed from exchange closures would imply coverage that does not exist. See what we hold.