Changing the Expiry Dates of Contracts

Highlight the contract that has the expiry date that you want the other contracts to have and right click on it (Step 1)
On the menu that appears left click on Select as Template (Step 2)

The Contract that you selected in the previous step is now in Dark Blue (Step 1)
Highlight the contracts you want to change the date of so they are in light blue then press right click on one of the contracts (Step 2)
In the menu that appears left click on Copy Template (Expiry/Due Date) to change the date (Step 3)

Answer yes to "Paste Expiry Date from Template" question and that will change the dates of the contracts. (Step 1)