Frank is revealed on 10/2/1988, Donnie is told the world will end in 28 days 6 hours 42 minutes and 12 seconds, Donnie is 16 years old

10+2+1988=2000

28+6+42+12=88

10-2=8, 9-1=8, 8 & 8 : 8 8 8 8

2x8=16, 6, 4+2=6, 12/2=6 : 16 6 6 6

6+6+6=18

Lots of 8's and 16's here...