The first day of a security being quoted Ex. The next business day following the record date.

The date on which shares change trading from 'cum' to 'ex' status. That is 'with' entitlement to 'without' entitlement.

The date, for a benefit event (eg a dividend) used to determine whether the buyer or seller of the security is entitled to the benefit. The ex date divides the cum period from the ex period. Bargains dealt prior to the ex date (during the cum period) are dealt with the benefit attached, unless stated to the contrary as a bargain condition. Bargains dealt after ex date (during the ex period) are dealt without the benefit attached, unless stated to the contrary by a bargain condition.