in two years 和two years later 都有‘ 两年后’ 的意思但它们的用法不同
in two years 常与一般将来时连用；
two years later 常与一般过去时连用。
如
He will graduate from university in two years.
两年后他将大学毕业。
He ran a clothes shop in 2003. Two years later he made a big success on business.
他2003年经营一家服装店。两年后他在上意上取得了很大的成功。
