This is the 5360th most frequent Russian word.
отмечен
Marked; noted; recognized.
Here 'отмечен' is used in its passive participle form, denoting that the day has been marked or designated on the calendar.
Этот день отмечен на календаре.
This day is marked on the calendar.
In this sentence, 'отмечен' is used to indicate that recognition was given to someone for a specific achievement.
Он был отмечен наградой за достижения в науке.
He was recognized with an award for achievements in science.
In this context, 'отмечено' is used impersonally to mean that a remark or observation was made about something during a discussion.