Board Thread:Questions and Answers/@comment-7890302-20141203213205/@comment-1386064-20150205234032

They were founded approximately 16 years before the beginning. Ban was imprisoned 20 years ago, and he was held captive for 4 years before meeting Meliodas. Also considering that the sins were framed 10 years before the story, this means the sins were formed and active at most 6 years, before being disbanded for 10 years.