ALT leagues?

In the league directory, there are two Auto Leagues listed as ALT8S21 and ALTSS10.

ALT8S21
Auto League 432217
Player Set: ANDY'S ALT8 SEASON 21

ALTSS10
Auto League 431855
Player Set: ANDY'S ALTS SEASON 10

Does anyone know (or have a good guess) what kind of league and player set this is? Thanks.

I am running 8 leagues that use those created pools. Alternate History Leagues, where managers take a franchise and manage it through the 20th Century in 4 or 5 season increments.

Andy's alts are on a 5-year cycle
Alt8S?? is on a 4 year cycle