一个很好的(复杂的!)底层公式和算法的来源是Jean Meeus的Astronomical Algorithms。
使用这些算法的PyMeeus实现,以及下面的代码,您可以获得2018年冬至(“冬季”指的是北半球)的以下值。
winter solstice for 2018 in Terrestrial Time is at:
(2018, 12, 21, 22, 23, 52.493725419044495)
winter solstice for 2018 in UTC, if last leap second was (2016, 12):
(2018, 12, 21, 22, 22, 43.30972542127711)
winter solstice for 2018 in local time, if last leap second was (2016, 12)
and local time offset is -7.00 hours:
(2018, 12, 21, 15, 22, 43.30973883232218)
i.e. 2018-12-21T15:22:43.309725-07:00
当然,答案并不精确到微秒级别,但我也想展示如何使用
arrow
进行高精度转换。
代码:
from pymeeus.Sun import Sun
from pymeeus.Epoch import Epoch
year = 2018
target="winter"
solstice_epoch = Sun.get_equinox_solstice(year, target=target)
print("%s solstice for %d in Terrestrial Time is at:\n %s" %
(target, year, solstice_epoch.get_full_date()))
print("%s solstice for %d in UTC, if last leap second was %s:\n %s" %
(target, year, Epoch.get_last_leap_second()[:2], solstice_epoch.get_full_date(utc=True)))
solstice_local = (solstice_epoch + Epoch.utc2local()/(24*60*60))
print("%s solstice for %d in local time, if last leap second was %s\n"
" and local time offset is %.2f hours:\n %s" %
(target, year, Epoch.get_last_leap_second()[:2],
Epoch.utc2local() / 3600., solstice_local.get_full_date(utc=True)))
使用非常酷的ISO和TZ感知模块
Arrow:Python更好的日期和时间,可以更好地打印。
import arrow
import math
slutc = solstice_epoch.get_full_date(utc=True)
frac, whole = math.modf(slutc[5])
print("i.e. %s" % arrow.get(*slutc[:5], int(whole), round(frac * 1e6)).to('local'))