Why is Metal Gear Solid 3 set in an older time period than Metal Gear Solid 2

The first half of Metal Gear Solid 2 is a few years after Metal Gear Solid 3 but the Riaden part is in 2009. Also it's a prequel starring Solid Snake's, and Liquid Snake's as well, father: Big Boss, althought he's known throughout the entire game as Naked Snake (his codename before earning the title of Big Boss). metal gear solid 3 is a prequel to all metal gears,mgs3 takes place in 1964 , the first part of mgs 2 takes place in 2007 second part takes place in 2009, mgs 1 takes place in2002