UTC和经度的本地太阳时功能

Question

我想知道是否有一个python函数/模块在给定UTC时间和经度的情况下计算午夜(或当地太阳时间)之后的当地时间？它不需要考虑夏令时.

提前致谢.

Answer 1

使用ephem的sidereal_time()方法:

import ephem # pip install pyephem (on Python 2)
             # pip install ephem   (on Python 3)

def solartime(observer, sun=ephem.Sun()):
    sun.compute(observer)
    # sidereal time == ra (right ascension) is the highest point (noon)
    hour_angle = observer.sidereal_time() - sun.ra
    return ephem.hours(hour_angle + ephem.hours('12:00')).norm  # norm for 24h

注意:ephem.hours是一个浮点数,表示以弧度表示的角度,并以字符串形式转换为"hh:mm:ss.ff".

为了比较,这里是"utc +经度"公式:

import math
from datetime import timedelta

def ul_time(observer):
    utc_dt = observer.date.datetime()
    longitude = observer.long
    return utc_dt + timedelta(hours=longitude / math.pi * 12)

例

from datetime import datetime

# "solar time" for some other cities
for name in ['Los Angeles', 'New York', 'London',
             'Paris', 'Moscow', 'Beijing', 'Tokyo']:
    city = ephem.city(name)
    print("%-11s %11s %s" % (name, solartime(city),
                             ul_time(city).strftime('%T')))

# set date, longitude manually
o = ephem.Observer()
o.date = datetime(2012, 4, 15, 1, 0, 2) # some utc time
o.long = '00:00:00.0' # longitude (you could also use a float (radians) here)
print("%s %s" % (solartime(o), ul_time(o).strftime('%T')))

产量

Los Angeles 14:59:34.11 14:44:30
New York    17:56:31.27 17:41:27
London      22:52:02.04 22:36:58
Paris       23:01:56.56 22:46:53
Moscow       1:23:00.33 01:07:57
Beijing      6:38:09.53 06:23:06
Tokyo        8:11:17.81 07:56:15
1:00:00.10 01:00:01

Answer 2

或者如果你想更短,你可以使用NOAA的低精度方程式:

#!/usr/local/bin/python

import sys
from datetime import datetime, time, timedelta
from math import pi, cos, sin

def solar_time(dt, longit):
    return ha

def main():
    if len(sys.argv) != 4:
        print 'Usage: hour_angle.py [YYYY/MM/DD] [HH:MM:SS] [longitude]'
        sys.exit()
    else:
        dt = datetime.strptime(sys.argv[1] + ' ' + sys.argv[2], '%Y/%m/%d %H:%M:%S')
        longit = float(sys.argv[3])

    gamma = 2 * pi / 365 * (dt.timetuple().tm_yday - 1 + float(dt.hour - 12) / 24)
    eqtime = 229.18 * (0.000075 + 0.001868 * cos(gamma) - 0.032077 * sin(gamma) \
             - 0.014615 * cos(2 * gamma) - 0.040849 * sin(2 * gamma))
    decl = 0.006918 - 0.399912 * cos(gamma) + 0.070257 * sin(gamma) \
           - 0.006758 * cos(2 * gamma) + 0.000907 * sin(2 * gamma) \
           - 0.002697 * cos(3 * gamma) + 0.00148 * sin(3 * gamma)
    time_offset = eqtime + 4 * longit
    tst = dt.hour * 60 + dt.minute + dt.second / 60 + time_offset
    solar_time = datetime.combine(dt.date(), time(0)) + timedelta(minutes=tst)
    print solar_time

if __name__ == '__main__':
    main()