it's a bug.
Thats a date bug,1970/1/1(1 january 1970) in a save doesn't mean that it was made at that date,TPT was made in 2008 by jacob1,so 1970 is to far away of TPT date creation
it wasn't made by Jacob1, original TPT was made by Skylark, Jacob1 does develop the game though
1970.1.1 would be expressed in almost all systems as 0b0000000000000000000000000000000000 or something like that. Essentially all time is measured as an amount of seconds away from the date 1970.1.1 If a save received that date then it was probably because the variable that stores creation date was corrupted.