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Noon (midday): civil time, solar noon, and cultural significance

Noon is the middle of the day. This article explains civil noon (clock time), solar noon (sun highest), historical measurement, cultural uses, and why clock noon and solar noon often differ.

Author: Leandro Alegsa Creation date: November 13, 2022 Last updated: June 2, 2026

simple.wikipedia.org · Public domain

Noon commonly refers to the middle of the day, the point when a civil clock reads 12:00. In the 24-hour system this is written as 12:00, while in the 12-hour system it is rendered as 12:00 PM. The word noon is often used interchangeably with midday, although "midday" can also mean the period around noon or the early afternoon rather than the single instant.

Solar noon and its meaning

Solar noon is an astronomical concept: it is the moment the Sun reaches its highest point in the sky for a given location on a particular day. Solar noon occurs roughly halfway between local sunrise and sunset. The traditional time reckoning terms ante meridiem (a.m.) and post meridiem (p.m.) derive from this notion of meridiem, the midday meridian.

Apparent position of the Sun

From most points in the Northern Hemisphere the Sun is due south at solar noon, while in the Southern Hemisphere it is due north, a relation tied to the observer's hemisphere and the Earth's tilt. On the Equator the Sun can be directly overhead at solar noon during the equinoxes. In locations near the Tropics the Sun can be overhead at solar noon on the relevant solstices: near the Tropic of Cancer in June and near the Tropic of Capricorn in December, with those latitudes defined approximately by latitude values of about 23.5° north and south and relating to the solstices.

Civil noon versus solar noon

Clock noon (12:00 by a civil clock) rarely matches solar noon. Modern societies use standard time regulated by time zones, and many countries apply daylight saving time, both of which shift clock readings away from local solar time. In addition, the Earth's elliptical orbit and axial tilt cause the Sun's apparent speed along the sky to vary; this produces the "equation of time," which also makes solar noon occur slightly before or after 12:00 civil time depending on the date.

History, measurement, and cultural roles

The measurement of noon has a long history. Sundials and meridian lines gave ancient and medieval observers a practical way to mark solar noon. Instruments such as transit telescopes later allowed precise determination for navigation, surveying and timekeeping. Culturally, noon is significant as a marker for daily rhythms: it often determines the midday meal, school and work schedules, public announcements like noon bells, and specific prayer times in various religious traditions.

Distinctions and notable facts

The opposite point of the day is midnight, twelve hours away.
Solar noon varies by longitude within a time zone and by date because of the equation of time.
Sundials show apparent solar time; civil clocks show standardized time that serves social and legal needs.
For many practical purposes — from legal definitions of dates to orienting solar panels — it matters whether one uses civil noon or solar noon.

For further reading on related concepts, see resources on the 24-hour clock (24-hour clock), the nature of the Sun (Sun), the equinox and solstice cycle (equinoxes, solstice), and the effects of timekeeping systems (time zones, daylight saving time). Additional technical or historical sources may be consulted via the links above for deeper detail.

View of Sesto in the Dolomites from the north, with the twelve of the Sesto sundial behind it in the south, above which the sun is at noon every day when seen from a location that lies on the same meridian, 12° 22′ east. (Painting by Konrad Petrides)

Astronomical noon

noon high

The elevation angle h of the sun at noon or its zenith distance z depends on the latitude B of the location and the seasonally varying declination δ of the sun:

h = 90° - z = 90° - |B - δ| (90° - B is the cob width or pole distance) z = 90° - h = |B - δ| with -23.45° ≤ δ ≤ +23.45°

For locations near the equator between the tropics (|B| < 23.45°), the sun passes exactly through the zenith twice a year; for locations within the polar circles, it is also below the horizon at "noon" for days to months at a time.

During the course of the day, the position of the sun and thus the shadows cast change depending on the arc of the day. It is shortest at noon, because now the sun reaches almost exactly its daily peak in upper culmination at the meridian passage with the noon altitude. The shadow of a rod as pointer (gnomon) of a sundial points north of the northern tropic exactly to the north, south of the southern tropic exactly to the south. Between the tropics, it depends on the season whether the shadow falls to the north or south at noon.

Time of the true noon

The time of the astronomical noon, the true noon, thus 12h true local time, depends on the one hand on the location and its geographical or astronomical longitude. On the other hand, the equation of time, which indicates the difference between true and mean local time (ZG = WOZ - MOZ), must also be taken into account in the calculation. This difference fluctuates several times in the course of a year due to the ecliptic slope and the elliptical shape of the Earth's orbit. At present it amounts to maximally +16 minutes, minimally -14 minutes. Four times a year the amount of the equation of time is zero and thus MOZ = WOZ; this was the case for the year 2019 on April 15, June 13, September 1, and December 25.

The changes in the equation of time from the previous day are each less than half a minute and are greatest shortly after the date of the winter solstice. At this time of year they are occasionally noticeable in the daily routine, because the light days are short and the changes in the duration of daylight are small. As the times of sunrise and sunset around the solstice receive special attention, it may be noted that they do not show a uniform pattern. In this connection, times referred to MOZ give the earliest sunset several days before, and the latest sunrise several days after, the date of the winter solstice, the day of shortest daylight duration. In all cases, however, the true noon is the middle of a bright day.

Specifically, the true noon can be calculated as follows:

Calculate the difference between the longitude of the observer and the longitude of the meridian for which zone time is defined; Central European Time is defined for MOZ at 15° East longitude.
Since the earth rotates from west to east, the further west the observation site lies, the later the sun reaches its peak. Because a solar day lasts 24 hours on average and the degree grid of the rotating Earth is divided into 360 degree lengths, there is a difference of 4 minutes per degree of longitude (1°) or 4 seconds per minute of arc (1′).
The calculated time difference is to be added to 12:00 if west of the zone time meridian, otherwise subtracted from 12:00.
The current value of the equation of time for the respective day can be taken from tables or calculated via a formula and subtracted from the already calculated time.
If daylight saving time applies, add one hour.

Calculation example for the city centre of Munich on geographical longitude 11.6° East on 12 July 2008 with equation of time ZG = -5 minutes in Central European Summer Time: 12:00 h + 0:04 h - (15 - 11.6) - (-0:05 h) + 1:00 h = 13:19 h CEST.

Noon in geophysics

In geophysics, magnetic and charge effects of the high atmosphere are strongly related to the time of day - e.g.

the magnetic Sq-variation and
the ion or electron density in the ionosphere (see also TEC), which reaches its maximum shortly after local noon, and
is also important for radio communications and cosmic geodesy (e.g. GPS and VLBI, monitored inter alia by regular measurement campaigns of the ITS).

Questions and Answers

Q: What is noon?

A: Noon is the time exactly halfway through the day (12.00-12:00 in the 24-hour clock and 12:00 PM-12:00 PM in the 12-hour clock).

Q: What does midday mean?

A: Midday also means noon, although this can also mean around noon or very early afternoon.

Q: What is solar noon?

A: Solar noon is when the sun appears highest in the sky compared to its positions during the rest of the day. It occurs when the Sun is exactly halfway between sunrise (dawn) and sunset.

Q: Where does solar noon occur at different times of year?

A: At solar noon, the sun is due south seen from the Northern Hemisphere, and due north seen from the Southern Hemisphere. The sun is directly overhead at solar noon at the Equator on equinoxes; at Tropic of Cancer (latitude 23½°N) on summer solstice in June; and at Tropic of Capricorn (23½°S) on winter solstice in December.

Q: How do time zones affect solar noon?

A: Because of use of time zones and daylight saving time, there may be a difference between when solar noon occurs and what a clock reads as "noon".

Q:What is opposite to Noon ? A:The opposite of Noon is Midnight