As a bill of exchange a post-dated cheque remains negotiable but it will not become a "cheque" till the date when it becomes "payable on demand".
and mainly revolves around section 138 of the Negotiable Instruments Act, 1881.
(3) For the purpose of determining whether a post-dated instrument is a cheque, the fact that the instrument is post-dated shall be disregarded.
(4) A cheque is not incomplete or irregular on its face by reason only that it is post-dated (whether or not the date has arrived).
If a Canadian financial institution inadvertently accepts and processes a cheque before the due date, the cheque writer may ask his or her financial institution to return the amount until the day before the cheque should have been cashed.