Exemption of long term capital gain u/s 54b

The date of acquisition and sale is that on the purchase and sale contract not the date of settlement.

You can enter into agreement to sell (not sale deed) with the buyer to whom you have sold the land on the date prior to the date of purchase of land. Just arrange a stamp paper of date prior to the date of purchase and complete the agreement to sell. In this way you are eligible to take the benefit of exemption.