Javascript or Python - How do I figure out if it's night or day?

Question

any idea how I figure out if it\'s currently night/day or sunrise/dawn based on time and location of the user?

I haven\'t found anything useful that I c

Answer 1

You can do as I did and use this public domain Sun.py module to compute the position of the sun relative to positions on the Earth. It's pretty old, but has worked well for me for many years. I made a few superficial modifications to it to be more up-to-date with Python 2.7, such as making the few classes in it new-style, but for the most part it's unchanged.

Here's one module I created, called sunriseset.py, which shows how to use it to calculate the sunrise and sunset times for a specific location given its geographic coordinates and timezone. The referenced timezone module is an implementation of the tzinfo abstract base class described in the datetime module's documentation on tzinfoobjects.

# -*- coding: iso-8859-1 -*-
import datetime
import timezone  # concrete tzinfo subclass based on the Python docs
import math
from Sun import Sun

__all__ = ['getsuninfo', 'Place']

class Place(object):
    def __init__(self, name, coords, tz=timezone.Pacific):
        self.name = name        # string
        self.coords = coords    # tuple (E/W long, N/S lat)
        self.tz = tz            # tzinfo constant

def _hoursmins(hours):
    """Convert floating point decimal time in hours to integer hrs,mins"""
    frac,h = math.modf(hours)
    m = round(frac*60, 0)
    if m == 60: # rounded up to next hour
        h += 1; m = 0
    return int(h),int(m)

def _ymd(date):
    """Return y,m,d from datetime object as tuple"""
    return date.timetuple()[:3]

def getsuninfo(location, date=None):
    """Return local datetime of sunrise, sunset, and length of day in hrs,mins)"""
    if date == None:
        querydate = datetime.date.today()
    else: # date given should be datetime instance
        querydate = date

    args = _ymd(querydate) + location.coords
    utcrise, utcset = Sun().sunRiseSet(*args)
    daylength = Sun().dayLength(*args)
    hrs,mins = _hoursmins(daylength)

    risehour, risemin = _hoursmins(utcrise)
    sethour, setmin   = _hoursmins(utcset)

    # convert times to timedelta values (ie from midnight utc of the date)
    midnight = datetime.datetime(tzinfo=timezone.utc, *_ymd(querydate))
    deltarise = datetime.timedelta(hours=risehour, minutes=risemin)
    utcdatetimerise = midnight+deltarise
    deltaset = datetime.timedelta(hours=sethour, minutes=setmin)
    utcdatetimeset  = midnight+deltaset

    # convert results from UTC time to local time of location
    localrise = utcdatetimerise.astimezone(location.tz)
    localset  = utcdatetimeset.astimezone(location.tz)

    return localrise, localset, hrs, mins

if __name__ == "__main__":
    import datetime, timezone

    def unittest(location, testdate):
        risetime, settime, hrs, mins = getsuninfo(location, testdate)

        print "Location:", location.name
        print "Date:", testdate.strftime("%a %x")
        print risetime.strftime("Sunrise %I:%M %p"), settime.strftime("- Sunset %I:%M %p (%Z)")
        print "daylight: %d:%02d" % (hrs,mins)
        print

    place = Place("My House", (-121.990278, 47.204444), timezone.Pacific)

    # test dates just before and after DST transitions
    print "pre 2007"
    print "========="
    unittest(place, datetime.date(2006, 4, 1))
    unittest(place, datetime.date(2006, 4, 2))
    unittest(place, datetime.date(2006, 10, 28))
    unittest(place, datetime.date(2006, 10, 29))

    print "2007"
    print "========="
    unittest(place, datetime.date(2007, 3, 10))
    unittest(place, datetime.date(2007, 3, 11))
    unittest(place, datetime.date(2007, 11, 3))
    unittest(place, datetime.date(2007, 11, 4))