This is the 13966th most frequent Swedish word.
årsdagen
The anniversary.
In this sentence, 'årsdagen' refers to the commemorative day marking a specific anniversary, in this case, of friendship.
Idag firar vi årsdagen av vår vänskap.
Today we celebrate the anniversary of our friendship.
Here, 'årsdagen' is used to denote the specific day marking the yearly recurrence of an event, in this case, his employment anniversary.
Årsdagen för hans anställning firades med en stor fest.
The anniversary of his employment was celebrated with a big party.
In this sentence, 'årsdagen' is used to express the yearly recurrence of the specific event of meeting for the first time.