This is the 1896th most frequent Korean word.
기간에
"During the period" or "within the period."
Here, '기간에' specifies the timeframe during which the issue was resolved.
그 점은 긴 휴가 기간에 해결되었습니다.
That issue was resolved during the long holiday period.
In this sentence, '기간에' denotes the specific time window for registration activities.
등록 기간에 신청 마감일을 주의하세요.
Pay attention to the application deadline during the registration period.
This usage shows '기간에' marking the time when the purchasing action took place.