Definition of 'Antedate'
A date entered on a legal contract or check that is prior to the actual date of occurrence. An antedate can sometimes be used if a contract has been delayed, to make sure the parties do not suffer from delays in the contract. Antedates can also be used illegally to benefit the parties involved by shifting dates in contracts to achieve more desirable terms.
Also known as "backdate".
Investopedia explains 'Antedate'
If an employee submits a form late for benefits, antedating the contract can be positive in that it protects the employee from losing benefits. On the other hand, antedating can also be used negatively. For example, since the strike price of executive stock options is based on the stock price that corresponds to the day of when these options are granted, the option grant date can be unethically antedated to a day in the past, where the stock's price was at a low for the benefit of the executives.