Augustus by Lang & Heyne: No More Forgotten Anniversary Excuses
A completely new indication, or indications, within an existing category of complications comes up only once in a blue moon. Until the Augustus, calendar complications consisted of indications for date, day, month, moon phase, annual calendars and perpetual calendars/leap year, tides, and astronomical elements such as star charts. That reads like a fairly comprehensive list, but none until now help to avoid the disappointment of forgetting a wedding anniversary or birthday.