I am attempting to edit a form created by someone for use on our website.

I need to change the date from 2015 to 2016.  It was created by our former Website Committee Chair.  I have his name, email address and the form number which shows up on the website.  How can I access the form to update it?

You can't update a form that belongs to someone else, unless they either (1) give you their password (so that you can login into their JotForm account), or if they (2) set you up as their sub user:

http://www.jotform.com/help/232-How-to-Share-Forms-with-a-Sub-Account-User

You otherwise cannot update a form which belongs to someone else.

If you cannot contact them for gaining access to their account or form, you can try to create a copy of their form by following this guide:

http://www.jotform.com/help/42-How-to-Clone-an-Existing-Form-from-a-URL

Then, you could make your desired changes on your cloned/copied version of their form, and simply publish/embed this new form into your website instead of the old form. The following guide helps with publishing your own form:

http://www.jotform.com/help/34-Adding-a-Form-to-a-Web-Page