Find websites by copyright year

Hello,

I saw it somewhere not long ago but totally forgot how to do it. So does anyone know how to search (google) for websites by their copyright year in the footer? I can't seem to figure it out. Is there a footer search like the allintext search?

Thanks

"Copyright *.com © 2010"
"Copyright *.net © 2012"
"Copyright *.org © 2013"
etc

not really what I was looking for but thank you. It will still give me copyright 2011-2017 if I search for 2011. Also forgot to mentioned that I would like it to be wordpress sites.