Hello Nikhil Mistry!

I am not sure, but you can choose test dates but not due date.

click on this link for further information!

https://khanacademy.zendesk.com/hc/en-us/community/posts/115000716391-How-to-Change-time-and-date this link could be helpful for you! 

Best Regards!

~Jessica.

I agree with Jessica! that link could be helpful for you!

Hi Nikhil,

It is currently only possible to change the due date for individual assignments----there is not a way to do this for multiple assignments at once. This is definitely something that is on our wishlist though!

Sorry I couldn't be of more immediate help! Please let me know if you have any additional questions!