Note: This calendar view maps the number of captures of https://accounts.google.com/ServiceLogin?hl=en&uilel=3&continue=https%253A%252F%252Fwww.youtube.com%252Fsignin%253Fnext%253D%25252Fupload%2526hl%253Den%2526feature%253Dredirect_login%2526app%253Ddesktop%2526action_handle_signin%253Dtrue&service=youtube&passive=true, not how many times the site was actually updated.
Look Up URL in general Internet Archive web collection.