Question

根据用户的时间和地点，我怎么知道当前是晚上/白天还是日出/黎明？

我还没有找到任何有用的东西，我可以在客户端或后端使用。

让小费变得棘手的是小时不是必须定义的，如果是白天和黑夜，这很大程度上取决于年，月，日，小时和地理坐标。

澄清......仿效这样的事情。

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一种近似的方法也非常有用。

希望有人可以提供帮助！

Answer 1

你可以像我一样做，并使用这个公共领域Sun.py模块来计算太阳相对于地球上位置的位置。它已经很老了，但多年来我一直很好用。我对它进行了一些表面修改，使其与Python 2.7更新，例如将其中的几个类改为新风格，但大多数情况下它都没有改变。

这是我创建的一个模块，名为sunriseset.py，它显示了如何使用它来计算特定位置的日出和日落时间，给出其地理坐标和时区。引用的timezone模块是tzinfo模块关于tzinfoobjects的文档中描述的{{3}}抽象基类的实现。

datetime

Answer 2

美国海军天文台提供了计算日出和日落算法的简明描述，可在此处获取：

http://edwilliams.org/sunrise_sunset_algorithm.htm

除了提供日期和位置外，您还需要选择一个天顶角（太阳将被视为“上升”或“设置”） - 链接的页面有多个选项。

<强>更新

由于链接页面不再可用，我在下面引用其文字。请注意，包含的公式是伪代码形式，而不是JavaScript。

Source:
    Almanac for Computers, 1990
    published by Nautical Almanac Office
    United States Naval Observatory
    Washington, DC 20392

Inputs:
    day, month, year:      date of sunrise/sunset
    latitude, longitude:   location for sunrise/sunset
    zenith:                Sun's zenith for sunrise/sunset
      offical      = 90 degrees 50'
      civil        = 96 degrees
      nautical     = 102 degrees
      astronomical = 108 degrees

    NOTE: longitude is positive for East and negative for West
        NOTE: the algorithm assumes the use of a calculator with the
        trig functions in "degree" (rather than "radian") mode. Most
        programming languages assume radian arguments, requiring back
        and forth convertions. The factor is 180/pi. So, for instance,
        the equation RA = atan(0.91764 * tan(L)) would be coded as RA
        = (180/pi)*atan(0.91764 * tan((pi/180)*L)) to give a degree
        answer with a degree input for L.


1. first calculate the day of the year

    N1 = floor(275 * month / 9)
    N2 = floor((month + 9) / 12)
    N3 = (1 + floor((year - 4 * floor(year / 4) + 2) / 3))
    N = N1 - (N2 * N3) + day - 30

2. convert the longitude to hour value and calculate an approximate time

    lngHour = longitude / 15

    if rising time is desired:
      t = N + ((6 - lngHour) / 24)
    if setting time is desired:
      t = N + ((18 - lngHour) / 24)

3. calculate the Sun's mean anomaly

    M = (0.9856 * t) - 3.289

4. calculate the Sun's true longitude

    L = M + (1.916 * sin(M)) + (0.020 * sin(2 * M)) + 282.634
    NOTE: L potentially needs to be adjusted into the range [0,360) by adding/subtracting 360

5a. calculate the Sun's right ascension

    RA = atan(0.91764 * tan(L))
    NOTE: RA potentially needs to be adjusted into the range [0,360) by adding/subtracting 360

5b. right ascension value needs to be in the same quadrant as L

    Lquadrant  = (floor( L/90)) * 90
    RAquadrant = (floor(RA/90)) * 90
    RA = RA + (Lquadrant - RAquadrant)

5c. right ascension value needs to be converted into hours

    RA = RA / 15

6. calculate the Sun's declination

    sinDec = 0.39782 * sin(L)
    cosDec = cos(asin(sinDec))

7a. calculate the Sun's local hour angle

    cosH = (cos(zenith) - (sinDec * sin(latitude))) / (cosDec * cos(latitude))

    if (cosH >  1) 
      the sun never rises on this location (on the specified date)
    if (cosH < -1)
      the sun never sets on this location (on the specified date)

7b. finish calculating H and convert into hours

    if if rising time is desired:
      H = 360 - acos(cosH)
    if setting time is desired:
      H = acos(cosH)

    H = H / 15

8. calculate local mean time of rising/setting

    T = H + RA - (0.06571 * t) - 6.622

9. adjust back to UTC

    UT = T - lngHour
    NOTE: UT potentially needs to be adjusted into the range [0,24) by adding/subtracting 24

10. convert UT value to local time zone of latitude/longitude

    localT = UT + localOffset

Answer 3

PyEphem 可用于计算下一个日出和日落的时间。在a blog post I found和the documentation of rise-set的基础上，您的问题可以解决如下。假设我是您的用户，我的位置为Oldenburg (Oldb), Germany。

import ephem

user = ephem.Observer()
user.lat = '53.143889'    # See wikipedia.org/Oldenburg
user.lon = '8.213889'     # See wikipedia.org/Oldenburg
user.elevation = 4        # See wikipedia.org/Oldenburg
user.temp = 20            # current air temperature gathered manually
user.pressure = 1019.5    # current air pressure gathered manually

next_sunrise_datetime = user.next_rising(ephem.Sun()).datetime()
next_sunset_datetime = user.next_setting(ephem.Sun()).datetime()

# If it is daytime, we will see a sunset sooner than a sunrise.
it_is_day = next_sunset_datetime < next_sunrise_datetime
print("It's day." if it_is_day else "It's night.")

# If it is nighttime, we will see a sunrise sooner than a sunset.
it_is_night = next_sunrise_datetime < next_sunset_datetime
print("It's night." if it_is_night else "It's day.")

备注

由于某种原因，lat和lon需要成为字符串，但如果它们是花车，则ephem不会抱怨。
为获得最佳效果，您可能需要获得当前的气温和气压。

先决条件

至少应该使用Python 2.7（带有pip-2.7 install pyephem）和Python 3.2（带有pip-3.2 install ephem）。

确保在系统上运行网络时间协议客户端。例如。在Debian Linux上：

$ sudo apt-get install ntp
$ sudo /etc/init.d/ntp start

确保在系统上设置了正确的时区。例如。在Debian Linux上：

$ sudo dpkg-reconfigure tzdata

Javascript或Python - 我如何判断它是晚上还是白天？

3 个答案:

备注

先决条件