put and call option Tag

Most transactions whether for the sale of property or a business include at least two or three important dates. These dates are:

1. The date that the contract is signed by the parties to that contract

2. The date that special conditions are satisfied

3. The date that the contract reaches settlement or completion. The completion date and the settlement date are different words, used to describe the same thing.

Which of these dates do authorities rely upon when determining the date of the sale?