To do something like it was done years ago.  Often, to wear clothing that was popular 10, 20 years ago.  This is common with sports teams, wearing uniforms from years past, on a "throwback Thursday."  It doesn't have to be a Thursday, but since there is alliteration, it is commonly used this way.

Just write "Throwback Thursday" in Google and open Wikipedia link. There is plenty of information about it.