1815 Kalenderwoche, a special model produced on the occasion of the 150th anniversary of Uhren Huber, Munich, at A. Lange & Söhne, with radial calendar week display on the outer rim of the dial
© A. Lange & Söhne
Unlike most other countries, Germany, for example, also often refers to the calendar week. It is the number of the week within the current year, i.e. from 1-52 or 53.
Only a few watch models display this value, including: