From the manufacturer:
the 29er Tag/Datum. Be it when sailing the 29er dinghy or creating its wristwatch counterpart, the new 29er Tag/Datum, it’s all about achieving the perfect balance. When the wind tugs at the sail at full force and crew members have to throw their entire weight into leaning out on the trapeze, the right balance is the deciding factor between winning or sinking. When designing the new 29er Tag/Datum, achieving a harmonious balance between the date and weekday displays was just as critical for our watch-making crew, albeit on dry land.