Complication · Calendar & astronomy
Month Indication
VerifiedA calendar display, usually a small subsidiary dial or aperture, showing the current month, generally as part of a triple (day-date-month) or perpetual calendar.
Definition
A calendar display, usually a small subsidiary dial or aperture, showing the current month, generally as part of a triple (day-date-month) or perpetual calendar.
Historical origin
A standard component of triple-calendar and perpetual-calendar watches from at least the nineteenth century onward; not usually offered as an isolated complication.
How it works
A twelve-position month disc or ring is advanced by one position at the end of each month, driven from the date-change mechanism's monthly rollover rather than from a separate daily source.
In a simple triple calendar, the month indication has no logic of its own and must be corrected manually alongside the date after short months; in a perpetual calendar, it is read and advanced correctly by the leap-year program wheel described under that complication.
Month indications are frequently combined mechanically and visually with a moon-phase display, sharing the same corrector and, in some designs, the same disc-advance mechanism.
Pocket watch context
A common element of nineteenth-century triple-calendar pocket watches, typically shown in a subsidiary dial alongside the day and paired with a date hand or ring.
Wristwatch context
Present in modern triple-calendar and perpetual-calendar wristwatches, usually as one of three or four subsidiary calendar indications on the dial.
Identification
- Twelve-position subsidiary dial or aperture, distinct from the seven-position day disc and 28–31 position date ring
- Correction behaviour indicates whether the underlying calendar is simple, annual or perpetual
Servicing notes
As with other calendar sub-mechanisms, correction during the change window can damage the jumper; specialist attention is recommended for any fault.
General guidance only. Complicated mechanisms should be assessed and serviced by a qualified watchmaker or clockmaker specialist, not adjusted at home.
Photographs
![Vacheron] How does this month indicator work? : r/Watches](/__l5e/assets-v1/3630b784-3061-4e64-a86c-30ab6fda3fb6/vacheron-how-does-this-month-indicator-work-r-watches.jpg)
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- de Carle, D., Watch and Clock Encyclopedia
Where sources disagree, the disagreement is stated rather than resolved silently.