Time Adjustments

Latitude selection

Sunrise and sunset times on any day vary with latitude. Below are the latitudes of a selection of European and North American cities, to the nearest five degrees, to help you choose which times to use.

55°N
Birmingham, Copenhagen, Dublin, Edinburgh, Edmonton, Moscow
50°N
Amsterdam, Berlin, Calgary, London, Paris, Seattle, Vancouver, Winnipeg
45°N
Bern, Bordeaux, Minneapolis, Milan, Ottawa
40°N
Athens, Denver, Madrid, New York, Rome, San Francisco, St Louis, Washington DC
35°N
Albuquerque, Atlanta, Dallas, Los Angeles, Memphis
30°N
Houston, New Orleans

Longitude adjustments

Sunrise, sunset and transit times are given in local standard time, and should be correct to within about half an hour for any location. If you want better accuracy you should adjust for your longitude within your time zone. The sunrise and sunset times listed are calculated for the central meridian of any time zone, ie for a longitude which is a multiple of 15°. Find your longitude and add/subtract 4 minutes for each degree by which you are west/east of the central meridian of your time zone.

For example, Salt Lake City is in the Mountain time zone, and located at approximately latitude 40°N and longitude 112°W, ie 7° west of the 105° meridian which runs through the Mountain time zone, so add 28 minutes to times for 40°N. If sunrise at 40°N is given as 5:30 then in Salt Lake it will be at about 5:58.

The rising and setting times of other bodies is given relative to the Sun. Although these can vary considerably even across the latitudes covered by The Night Sky, they will still give a reasonable idea of when a body will be visible. Transit times are used in preference, as these are the same at all latitudes.

Time zone conversions

Times of global events (such as moon phases and lunar eclipses) are given in Universal Time (UT). For all time zones other than GMT, and whenever daylight saving time is in force, they will require a simple conversion. Here are some examples -

Universal Time / Greenwich Mean Time 0 8pm 9pm 10pm 11pm 12am 1am 2am 3am 4am 5am 6am 7am
Middle European Time / British Summer Time +1 9pm 10pm 11pm 12am 1am 2am 3am 4am 5am 6am 7am 8am
Eastern European Time / Middle European Daylight Time +2 10pm 11pm 12am 1am 2am 3am 4am 5am 6am 7am 8am 9am
Eastern European Daylight Time +3 11pm 12am 1am 2am 3am 4am 5am 6am 7am 8am 9am 10am
Atlantic Daylight Time -3 5pm 6pm 7pm 8pm 9pm 10pm 11pm 12am 1am 2am 3am 4am
Atlantic Standard Time / Eastern Daylight Time -4 4pm 5pm 6pm 7pm 8pm 9pm 10pm 11pm 12am 1am 2am 3am
Eastern Standard Time / Central Daylight Time -5 3pm 4pm 5pm 6pm 7pm 8pm 9pm 10pm 11pm 12am 1am 2am
Central Standard Time / Mountain Daylight Time -6 2pm 3pm 4pm 5pm 6pm 7pm 8pm 9pm 10pm 11pm 12am 1am
Mountain Standard Time / Pacific Daylight Time -7 1pm 2pm 3pm 4pm 5pm 6pm 7pm 8pm 9pm 10pm 11pm 12am
Pacific Standard Time -8 12pm 1pm 2pm 3pm 4pm 5pm 6pm 7pm 8pm 9pm 10pm 11pm
Hawaii Standard Time -10 10am 11am 12pm 1pm 2pm 3pm 4pm 5pm 6pm 7pm 8pm 9pm

Glossary of Terms

Aphelion The point where a body's orbit is furthest from the Sun. It will be travelling at its slowest at this point.
Blue Moon Not a strict astronomical term. Refers to a second Full Moon within one month, which generally occurs once every few years. A much rarer event is a month with no Full Moon at all. This can only happen in February, and prior to 1999 last hapened 1961.
Conjunction When a body comes into line with another as seen from the Earth. Usually, by default, with the sun - superior conjunction being when the body is on the far side of the sun, inferior conjunction when it is on the near side. Mercury and Venus are the only planets capable of inferior conjunctions.
Degrees The width of your finger tip, held at arm's length, is roughly one degree of arc. The knuckle of your thumb represents about two degrees, and the width of your fist about ten degrees. The distance between the tips of your thumb and little finger, spread wide, is around twenty degrees. The "pointers" in Ursa Major are about five degrees apart.
Direct The normal, eastward apparent motion of an outer planet as opposed to retrograde motion.
Eclipse, Lunar This occurs when the Earth's shadow is cast onto the Moon. It will happen at the time of the full moon, and will be visible from the entire night-side of the Earth. During an umbral eclipse, when all or part of the Moon passes through the darker central cone of shadow (equivalent to a total solar eclipse) the affected portion may be coloured anything from almost black through deep red to pale orange. In a penumbral eclipse, the Moon enters the lighter outer shadow (corresponding to a partial solar eclipse). This will generally be a pale amber or yellow colour.
Eclipse, Solar This is when the Moon's shadow is cast onto the Earth. It will take place during the new moon, and is only visible from places lying in the path of the shadow. The time, duration and nature of the eclipse will vary with location. A partial eclipse occurs when the Earth enters the lighter outer shadow of the Moon - the penumbra. When the dark central cone of the lunar shadow - the umbra - crosses the Earth's surface, a total eclipse will be observed from that region. Occasionally, when the Moon is near apogee (its furthest point from Earth), the umbra will fall short and a ring-shaped annular eclipse will be visible at the centre of the shadow.
Ecliptic All of the planets and most of the other bodies in the Solar System move within one plane. When seen from the Earth, they all appear to move within about three degrees of a line, inclined to the equator, which is called the Ecliptic.
Elongation Particularly of Mercury and Venus, the apparent separation between the planet and the Sun. Maximum elongations alternate with conjunctions.
Gibbous Moon The phase between quarter and full when most of the Moon's disc is illuminated.
Equinox Literally "equal night" - the time in the Earth's year when the Sun crosses the equator and day and night are of equal duration. Sunrise and sunset are at the same time at all latitudes. This takes place during the spring (vernal equinox) and autumn/fall (autumnal equinox).
Evening Object A planet which transits before midnight.
Full Moon When the Moon is in the opposite side of the sky to the sun, and it appears as a full disc from the Earth.
Magnitude The apparent brightness of an object. The lower the magnitude, the brighter the object, so magnitude 1 is brighter than magnitude 2, while magnitude -1 is brighter still. Sirius, the brightest star, has a magnitude of -1.4. The limit of naked eye visibility is about 6.
Morning Object A planet which transits after midnight.
Nadir The exact opposite of the zenith - the celestial point directly beneath the observer's feet, and thus somewhat obscured by the Earth!
New Moon When the Moon is in the same side of the sky as the Sun, and only its dark side is visible from the Earth.
Opposition The point where a planet is on the opposite side of the Earth to the Sun, and it is probably at its brightest. Mercury and Venus cannot come into opposition.
Perihelion The point where a body's orbit comes closest to the Sun. It will be travelling at its fastest at this point.
Quarter Moon When the Moon is at right angles to the Sun and Earth, and appears as a semi-circle from the Earth.
Radiant The point in the sky from which a meteor shower appears to originate. It is a perspective effect caused by the relative movement of the Earth and the meteoritic particles.
Retrograde The westward apparent motion of an outer planet when the Earth's movement around the Sun overtakes it.
Stationary point The point where an outer planet changes between direct motion and retrograde motion.
Solstice The time in the Earth's year when the Sun reaches its greatest distance from the equator, and day and night are at their longest or shortest. There is one in the summer and one in the winter.
Transit (1) The point midway between the rising and the setting of a body when it is crosses an imaginary line running from the north pole to the south pole via the zenith. At this moment it is at its highest in the sky.
Transit (2) When either Mercury or Venus passes directly between the Earth and the Sun, and appears as a silhouette against the solar disc - a rare event. The next transit of Mercury is on 15^th November 1999, and the next of Venus (the first since 6^th December 1882) is on 8^th June 2004.
Zenith The point in the sky directly above the observer's head, ie declination 90°.

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Aphelion	The point where a body's orbit is furthest from the Sun. It will be travelling at its slowest at this point.
Blue Moon	Not a strict astronomical term. Refers to a second Full Moon within one month, which generally occurs once every few years. A much rarer event is a month with no Full Moon at all. This can only happen in February, and prior to 1999 last hapened 1961.
Conjunction	When a body comes into line with another as seen from the Earth. Usually, by default, with the sun - superior conjunction being when the body is on the far side of the sun, inferior conjunction when it is on the near side. Mercury and Venus are the only planets capable of inferior conjunctions.
Degrees	The width of your finger tip, held at arm's length, is roughly one degree of arc. The knuckle of your thumb represents about two degrees, and the width of your fist about ten degrees. The distance between the tips of your thumb and little finger, spread wide, is around twenty degrees. The "pointers" in Ursa Major are about five degrees apart.
Direct	The normal, eastward apparent motion of an outer planet as opposed to retrograde motion.
Eclipse, Lunar	This occurs when the Earth's shadow is cast onto the Moon. It will happen at the time of the full moon, and will be visible from the entire night-side of the Earth. During an umbral eclipse, when all or part of the Moon passes through the darker central cone of shadow (equivalent to a total solar eclipse) the affected portion may be coloured anything from almost black through deep red to pale orange. In a penumbral eclipse, the Moon enters the lighter outer shadow (corresponding to a partial solar eclipse). This will generally be a pale amber or yellow colour.
Eclipse, Solar	This is when the Moon's shadow is cast onto the Earth. It will take place during the new moon, and is only visible from places lying in the path of the shadow. The time, duration and nature of the eclipse will vary with location. A partial eclipse occurs when the Earth enters the lighter outer shadow of the Moon - the penumbra. When the dark central cone of the lunar shadow - the umbra - crosses the Earth's surface, a total eclipse will be observed from that region. Occasionally, when the Moon is near apogee (its furthest point from Earth), the umbra will fall short and a ring-shaped annular eclipse will be visible at the centre of the shadow.
Ecliptic	All of the planets and most of the other bodies in the Solar System move within one plane. When seen from the Earth, they all appear to move within about three degrees of a line, inclined to the equator, which is called the Ecliptic.
Elongation	Particularly of Mercury and Venus, the apparent separation between the planet and the Sun. Maximum elongations alternate with conjunctions.
Gibbous Moon	The phase between quarter and full when most of the Moon's disc is illuminated.
Equinox	Literally "equal night" - the time in the Earth's year when the Sun crosses the equator and day and night are of equal duration. Sunrise and sunset are at the same time at all latitudes. This takes place during the spring (vernal equinox) and autumn/fall (autumnal equinox).
Evening Object	A planet which transits before midnight.
Full Moon	When the Moon is in the opposite side of the sky to the sun, and it appears as a full disc from the Earth.
Magnitude	The apparent brightness of an object. The lower the magnitude, the brighter the object, so magnitude 1 is brighter than magnitude 2, while magnitude -1 is brighter still. Sirius, the brightest star, has a magnitude of -1.4. The limit of naked eye visibility is about 6.
Morning Object	A planet which transits after midnight.
Nadir	The exact opposite of the zenith - the celestial point directly beneath the observer's feet, and thus somewhat obscured by the Earth!
New Moon	When the Moon is in the same side of the sky as the Sun, and only its dark side is visible from the Earth.
Opposition	The point where a planet is on the opposite side of the Earth to the Sun, and it is probably at its brightest. Mercury and Venus cannot come into opposition.
Perihelion	The point where a body's orbit comes closest to the Sun. It will be travelling at its fastest at this point.
Quarter Moon	When the Moon is at right angles to the Sun and Earth, and appears as a semi-circle from the Earth.
Radiant	The point in the sky from which a meteor shower appears to originate. It is a perspective effect caused by the relative movement of the Earth and the meteoritic particles.
Retrograde	The westward apparent motion of an outer planet when the Earth's movement around the Sun overtakes it.
Stationary point	The point where an outer planet changes between direct motion and retrograde motion.
Solstice	The time in the Earth's year when the Sun reaches its greatest distance from the equator, and day and night are at their longest or shortest. There is one in the summer and one in the winter.
Transit (1)	The point midway between the rising and the setting of a body when it is crosses an imaginary line running from the north pole to the south pole via the zenith. At this moment it is at its highest in the sky.
Transit (2)	When either Mercury or Venus passes directly between the Earth and the Sun, and appears as a silhouette against the solar disc - a rare event. The next transit of Mercury is on 15^th November 1999, and the next of Venus (the first since 6^th December 1882) is on 8^th June 2004.
Zenith	The point in the sky directly above the observer's head, ie declination 90°.