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.
The post-dated cheque is not payable till the date which is shown on the face of the said document.
It will only become cheque on the date shown on it and prior to that it remains a bill of exchange under Section 5 of the Act.
In the United States and the UK, post-dated cheques are negotiable instruments and can be drawn upon at any time, while in India and Australia post-dated cheques are not payable until the date written on the cheque. (1) Where a cheque, or any indorsement of a cheque, is dated, the date shall, unless the contrary is proved, be presumed to be the day on which the cheque was drawn or the indorsement made, as the case may be.
(2) A cheque is not invalid by reason only that- (a) it is not dated; (b) it is antedated or post-dated; or (c) the date it bears is a Sunday.
A Canadian bank, for example, is not supposed to process a post-dated cheque and if it does so by mistake, the cheque writer may ask their bank to correct the error.
(f(4)) "The presentation of a postdated check is not subject to the civil or penal sanctions" that would normally apply to someone who wrote a check with insufficient funds because the postdated check promises "to discharge a present obligation at a future date" and that money would be available to meet the debt when the check is cashed.