This is the 267th most frequent Japanese word.
当時
"At that time" or "in those days."
In this example, '当時' relates to a specific past period of youth, giving a timeframe for the experiences.
彼女は若かった当時に多くの経験をしました。
She had many experiences during the time she was young.
In this sentence, '当時' is used to set a past time context for the statement about being a student. It indicates a specific past period referenced.
当時、私は学生でした。
At that time, I was a student.
Here, '当時' clarifies the temporal setting of the action (being abroad) in relation to the mentioned incident.