This post reminds me of the song from my favorite Korean R&B singer 일년 이면 (ilyon imyon) which literally means One Year Passed but the English title is official A Year Has Passed. Learning about numbers made me realize that 일년 does no necessarily mean year alone.
Anyway similar to how weeks are counted, both Native and Sino-Korean numbers can be used to count years, the only difference is the marker. For Native Korean numbers it is followed by the marker 해 (hae) and for Sino-Korean number it’s 년 (nyon). So to say 2 years in Korean one may be able to hear 두해 (du hae) or 이년 (inyon).
However, it’s more common to hear counting of years using the Sino-Korean numbers rather than the native ones when its more than 2 years.
It Started with Hangul 