ex dates

[MarcusRainbow]

Every instrument should have an ex date, at least optionally. Even cash and stock should have an optional ex date, in case they are the result of some transfer to a third party.

Closely associated with a fixing table, maybe contained within it, should be a date after which any payments that are ex should not be included. This is normally the same as the spot date. However, during theta calculation, it may optionally be left where it is, while the spot date is bumped forward. This has the effect of leaving all payments in the same ex state, which means there should be no large jumps due to the theta bump.