Under GST point of taxation is at the time of supply.
How to determine time of supply
The time of supply of goods shall be the earlier of the following dates:
(a) The date of issuing of invoice (or the last day by which invoice should have been issued)
(b) The date of receipt of payment
-whichever is earlier
You should not worry about manufacturing date, and if you are receiving advance pls. check notifications regarding applicability of GST on advance because we have multiple notification regarding GST on advance receipt.
Regards, CA Guru Manohar