Hi,
Thank you for choosing Windows and thanks for providing us an opportunity to assist you.
As per the description, you are having query about the activation date of Windows XP after 2014.
You can go ahead and Install and activate Windows XP after 2014. Only the Support option would not be there after 2014 for Windows XP.
Reply to us if you face any issues with Activation or any other Windows Issue, and we would be glad to assist you.
Have a nice day!
Hope this information helps.