exemple: this website http://animagefestival.com/2017/

you can access all former years of festival versions. each is greatly different from another. and each year is accessable by the festival domain slash the year

http://animagefestival.com/2016/
http://animagefestival.com/2015/
http://animagefestival.com/2018/

...

HOW DO YOU DO THAT?
is it done by a PLUG IN?
can somebody help me?

thank you so much!!!