noons

Noons, in plural form, refer to the midday moments across days and places. In everyday use, noon most often denotes solar noon, the moment when the Sun reaches its highest point in the sky for a given location. Solar noon occurs as the Sun crosses the local meridian. Because the Sun’s path is not perfectly uniform and time zones vary, the clock time of noon often does not match true solar noon.

The difference between clock noon and solar noon is governed by the equation of time, which accounts for the eccentricity of Earth’s orbit and the tilt of its axis. The discrepancy can be a matter of seconds or as much as about 14 minutes over the course of a year. Civil time reads noon according to standard time zones and may be shifted by daylight saving time, so civil noon is not always near solar noon in a given location.

Culturally and historically, noon has held various significances. In many languages, noon is simply 12:00 PM, but it has also figured in calendars, religious practices, and daily routines. In navigation, the determination of solar noon was important for estimating longitude before accurate chronometers were available. The expression high noon has entered popular culture to signify the middle of the day or a critical moment.

In practice, solar noon can be measured with sundials, astronomical observations, or precise timekeeping systems that reference Coordinated Universal Time. Related concepts include local apparent noon, mean solar noon, and the use of clock time versus solar time in different regions.