This is the 522nd most frequent Estonian word.
aastatel
"during the years"
Here, 'aastatel' specifies the duration of time, denoting the period in which their residence took place.
Minu vanemad elasid Hollandis aastatel 1985–1990.
My parents lived in the Netherlands during the years 1985–1990.
The word 'aastatel' here is used to signify a specific range of years when an event took place.
Aastatel 1940–1945 puhkes Euroopas suur sõda.
During the years 1940–1945, a great war broke out in Europe.
In this context, 'aastatel' means 'within the years,' marking the temporal span of when the study occurred.