WordNet

light during the daytime
time during which clocks are set one hour ahead of local standard time; widely adopted during summer to provide extra daylight in the evenings (同)daylight-savings time, daylight saving, daylight savings

PrepTutorEJDIC

『日光』,昼の光 / 夜明け / 公然,周知・「… the living daylights out of誰々」で「誰々をこてんぱんに…する」
『昼間』
「動詞 + living daylights out of誰々」の成句で、「誰々をこっぴどく…する」
夏時間{略}『DST,D.S.T.』(《おもに英》summer time)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/05/10 04:46:28」(JST)

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For other uses, see Daylight (disambiguation).

World map showing the areas of the Earth receiving daylight around 13:00 UTC, April 2nd.

Daylight or the light of day is the combination of all direct and indirect sunlight outdoors during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected from the Earth and terrestrial objects. Sunlight scattered or reflected from objects in outer space (that is, beyond the Earth's atmosphere) is generally not considered daylight. Thus, moonlight is never considered daylight, despite being "indirect sunlight". Daytime is the period of time each day when daylight occurs.Daylight happens because the earth rotates and either side the sun shines on is considered daylight.

Definition [edit]

Daylight is present at a particular location, to some degree, whenever the sun is above the horizon at that location. (This is true for slightly more than 50% of the Earth at any given time. For an explanation of why it is not exactly half, see here). However, the outdoor illuminance can vary from 120,000 lux for direct sunlight at noon, which may cause eye pain, to less than 5 lux for thick storm clouds with the sun at the horizon (even <1 lux for the most extreme case), which may make shadows from distant street lights visible. It may be darker under unusual circumstances such as a solar eclipse or very high levels of atmospheric smoke (See New England's Dark Day), dust,^[1] or volcanic ash.^[2]

Daylight intensity in different conditions [edit]

Illuminance	Example
120,000 lux	Brightest sunlight
110,000 lux	Bright sunlight
20,000 lux	Shade illuminated by entire clear blue sky, midday
10,000 - 25,000 lux	Typical overcast day, midday
<200 lux	Extreme of darkest storm clouds, midday
400 lux	Sunrise or sunset on a clear day (ambient illumination).
40 lux	Fully overcast, sunset/sunrise
<1 lux	Extreme of darkest storm clouds, sunset/rise

For comparison, nighttime illuminance levels are:

Illuminance	Example
<1 lux	Moonlight^[3]
0.25 lux	Full Moon on a clear night^[4]^[5]
0.01 lux	Quarter Moon
0.002 lux	Starlight clear moonless night sky including airglow^[4]
0.0002 lux	Starlight clear moonless night sky excluding airglow^[4]
0.00014 lux	Venus at brightest^[4]
0.0001 lux	Starlight overcast moonless night sky^[4]

For a table of approximate daylight intensity in the Solar System, see sunlight.

Effects [edit]

Daylight in January. At the polar regions there are extreme differences in the amount of daylight in summer and winter.

Daylight is widely accepted to have a positive psychological effect on the human being,^{[citation needed]} and consequently more cases of mental health problems are registered during the winter months than during the summer months due to the shortened periods of daylight.^{[citation needed]} Cases of depression specifically linked to limited daylight are referred to as seasonal affective disorder.

Daylighting is lighting an indoor space with openings such as windows and skylights that allow daylight into the building. This type of lighting is chosen to save energy, to avoid hypothesized adverse health effects of over-illumination by artificial light, and also for aesthetics. The amount of daylight received into an indoor space or room is defined as a daylight factor, being the ratio between the measured internal and external light levels. Artificial lighting energy use can be reduced by simply installing fewer electric lights because daylight is present, or by dimming/switching electric lights automatically in response to the presence of daylight, a process known as daylight harvesting.

In recent years, work has taken place to recreate the effects of daylight artificially. This is however expensive in terms of both equipment and energy consumption and is applied almost exclusively in specialist areas such as filmmaking, where light of such intensity is required anyway.

Notes [edit]

^ http://www.perryton.com/black.htm
^ http://volcanoes.usgs.gov/ash/
^ Bunning, Erwin; and Moser, Ilse (April 1969). "Interference of moonlight with the photoperiodic measurement of time by plants, and their adaptive reaction" (– ^{Scholar search}). Proceedings of the National Academy of Sciences of the United States of America 62 (4): 1018–1022. Bibcode:1969PNAS...62.1018B. doi:10.1073/pnas.62.4.1018. PMC 223607. PMID 16591742. Retrieved 2006-11-10. ^{[dead link]}
^ ^a ^b ^c ^d ^e Paul Schlyter, Radiometry and photometry in astronomy FAQ (2006)
^ "Petzl reference system for lighting performance". Archived from the original on 2008-06-20. Retrieved 2007-04-24.

External links [edit]

Royal Institution of Chartered Surveyors - Rights to Light Determination Homepage
Daylight Chart shows sunrise and sunset times in a chart, for any location in the world.
http://www.gandraxa.com/length_of_day.xml Deriving the formulas to calculate the length of day.

UpToDate Contents

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1. 季節性情動障害 seasonal affective disorder
2. 時差ぼけ jet lag
3. メラトニンの生理学および臨床使用 physiology and clinical use of melatonin
4. パルスオキシメトリ pulse oximetry
5. サシガメ（サシガメ属）による咬傷に対する反応 reactions to bites from kissing bugs triatoma

English Journal

Daytime triglyceride variability in men and women with different levels of triglyceridemia.

Klop B, Cohn JS, van Oostrom AJ, van Wijk JP, Birnie E, Cabezas MC.SourceDpts. of Internal Medicine, Sint Franciscus Gasthuis Rotterdam, The Netherlands.
Clinica chimica acta; international journal of clinical chemistry.Clin Chim Acta.2011 Nov 20;412(23-24):2183-9. Epub 2011 Aug 12.
BACKGROUND: Triglyceride (TG) levels measured in either the fasting or non-fasting state predict the risk of cardiovascular disease (CVD). Since CVD risk assessment is affected by variability in TG, the aim of the study was to investigate intra-individual variability of non-fasting TG.METHODS: Capil
PMID 21864522

Testing acuity and contrast vision under standardised lighting conditions.

Durst W, Peters T, Wilhelm B.SourceSTZ eyetrial at the Centre for Ophthalmology, Schleichstrase 12-16, 72076 Tubingen, Germany; wilhelm.durst@stz-eyetrial.de.
The British journal of ophthalmology.Br J Ophthalmol.2011 Nov;95(11):1506-8. Epub 2011 Jul 6.
Aims The aim of this work was to construct a lighting device that allows a uniform lighting of top illumination charts, as used for the examination of contrast vision and visual acuity. The relevant standards make strict demands for such charts with regard to the quality of the lighting, the absolut
PMID 21733917

Japanese Journal

An Intelligent Lighting System to Realize Individual Lighting Environments Based on Estimated Daylight Distribution

Mitsunori Miki,Takuro Yoshii,Tomoyuki Hiroyasu,Masato Yoshimi,Hiroyuki Yonemoto
情報処理学会研究報告. MPS, 数理モデル化と問題解決研究報告 2011-MPS-84(7), 1-6, 2011-07-11
… This system uses illuminance sensors for measuring not the illuminance on workplanes but that of daylight: it optimizes lighting based on simulations for different luminous intensities of lighting and patterns of daylight illuminance distribution which are estimated from measurements by daylight illuminance sensors. …
NAID 110008583475

照明の実際-10 温暖地域のオフィスビルの昼光利用における窓の大きさの影響,アルジェリアのビスクラの場合

森本一成
照明学会誌 95(6), 330-331, 2011-06-01
NAID 110008662063

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