Saudi Luxury / Watch basics
Day-date, moonphase, annual and perpetual calendars
Compare calendar watches by how often you must correct them, so you can choose the one that suits how often you wear it.
Calendar watches differ mainly in how often you must correct them: a date or day-date after every month shorter than 31 days, an annual calendar once a year, and a perpetual calendar not until 2100, as long as it keeps running.
| Calendar | What it shows | Corrections you make |
|---|---|---|
| Date or day-date | Date, plus weekday on a day-date | Five a year, after February, April, June, September and November |
| Big date | The date in large numerals | Five a year, as for a simple date |
| Complete (triple) calendar | Day, date and month | Five a year, as for a simple date |
| Annual calendar | Date, usually day and month | One a year, on 1 March |
| Perpetual calendar | Date, day, month and leap year | None until 1 March 2100 |
| Moonphase | The moon’s phase | About one day every two and a half years on a simple display |
Date, day-date and complete calendars
The Seiko 5 Sports Field HDB006K1 shows both day and date at the affordable end; the Rolex Day-Date 18238 does the same in yellow gold. On a watch with a quick-set date, each correction takes seconds.
A big date splits the tens and units across two separate discs or rings so the date reads larger. A complete, or triple, calendar adds the month. Neither knows month lengths, so both need the same five corrections as a simple date.
Annual and perpetual
An annual calendar knows which months have 30 days and which have 31, and needs help only at the end of February. The Patek Philippe Annual Calendar 5396G-011 is a well-known example. A perpetual calendar also tracks leap years. Its only scheduled correction falls in 2100, which is not a leap year. For the full detail, Watch Codex explains how a perpetual calendar tracks leap years.
The catch with mechanical versions is the power reserve. The Patek runs for 45 hours; leave it off the wrist for two days and it stops, and you then reset the time, day, date and month. On a perpetual, resetting can mean advancing through many months. A quartz perpetual avoids this: the Seiko Premier Quartz Perpetual Calendar SNQ157 keeps running on its battery whether you wear it or not.
Moonphase
A moonphase shows the moon’s current shape, set by hand to match the sky. It is not a Hijri date display, and it does not tell you when a month begins. You can have one on a quartz watch, such as the Swatch x Omega Bioceramic Moonphase chronograph, or on a mechanical chronograph from the Longines Master Collection. Browse all moonphase watches on the site.
You can reset it at home. Many use a small recessed corrector on the case side, pressed with the tool supplied; some use a crown position. Set the display to full moon, then advance it one step for each day since the last full moon. If the corrector resists, stop and have it checked rather than forcing it.
Setting the date safely
On many mechanical calendars, the date mechanism engages for several hours around midnight. Most makers advise against changing the date while the hands are in that window, often given as roughly 9 pm to 3 am. A safe routine for a stopped watch:
- Turn the hands to about 6 o’clock, then quick-set the date to yesterday’s.
- Turn the hands forward through midnight until the date changes, then on to the correct time, so the watch also shows the right half of the day.
Check the manual for your watch, since some differ.