What does Dies mean?

The association turned fifty this year, so the dies was celebrated extra big.

Dutch student slang. This is a Dutch word. You will hear it a lot at Dutch universities, student associations and in student houses.

Dies Natalis is Latin for birthday. The day is often celebrated with a borrel or party. When it is a big round anniversary it often turns into a lustrum, with a whole week of festivities. Also read about dispuut and constitutieborrel.