#!/usr/bin/python
# Julian calendar calculations for calculating the position of the sun relative to the earth
# Copyright 2008 Brandon Stafford
#
# This file is part of Pysolar.
#
# Pysolar is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# Pysolar is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with Pysolar. If not, see <http://www.gnu.org/licenses/>.
import math
def GetJulianCentury(julian_day):
return (julian_day - 2451545.0) / 36525.0
def GetJulianDay(utc_datetime): # based on NREL/TP-560-34302 by Andreas and Reda
# does not accept years before 0 because of bounds check on Python's datetime.year field
year = utc_datetime.year
month = utc_datetime.month
if(month <= 2.0): # shift to accomodate leap years?
year = year - 1.0
month = month + 12.0
day = utc_datetime.day + (((utc_datetime.hour * 3600.0) + (utc_datetime.minute * 60.0) + utc_datetime.second + (utc_datetime.microsecond / 1000000.0)) / 86400.0)
gregorian_offset = 2.0 - (year // 100.0) + ((year // 100.0) // 4.0)
julian_day = math.floor(365.25 * (year + 4716.0)) + math.floor(30.6001 * (month + 1.0)) + day - 1524.5
if (julian_day <= 2299160.0):
return julian_day # before October 5, 1852
else:
return julian_day + gregorian_offset # after October 5, 1852
def GetJulianEphemerisCentury(julian_ephemeris_day):
return (julian_ephemeris_day - 2451545.0) / 36525.0
def GetJulianEphemerisDay(julian_day, delta_seconds = 66.0):
"""delta_seconds is value referred to by astronomers as Delta-T, defined as the difference between
Dynamical Time (TD) and Universal Time (UT). In 2007, it's around 65 seconds.
A list of values for Delta-T can be found here: ftp://maia.usno.navy.mil/ser7/deltat.data"""
return julian_day + (delta_seconds / 86400.0)
def GetJulianEphemerisMillenium(julian_ephemeris_century):
return (julian_ephemeris_century / 10.0)
) is private.
