Am I missing something или did Anderson make a big mess up in the time line when Письмо Afterlife?? According to the Назад movies&my math at the begining of the movie when it says "four years later" it should be SIX!!???

Alice makes it clear upon meeting up w/ clair again its been a год and half sence getting the chopper in the desert. And when finding clair in alaska its six months after the attack on the Япония facility.so from this Ты can see it took alice and her clones a год to reach japan. If Ты do the math w/ the first three films Ты know its been 5years allready at the end of extinction.add a год and Ты got SIX!!!!??