Calculate length of day change over the year

daychange.py

import ephem
import datetime

# ephem.localtime(ephem.next_summer_solstice('2019-1-1'))

s = ephem.Sun()
o = ephem.city('Boston')
yesterday_len = 0
for i in range(0, 365):
  d = datetime.datetime(2019,1,1,16,0) + datetime.timedelta(i)
  o.date = d
  daylen = o.next_setting(s) - o.previous_rising(s)
  #print("{},{},{}".format(d, o.previous_rising(s), o.next_setting(s), (daylen-yesterday_len)))
  print("{},{}".format(d, (daylen-yesterday_len)))
  yesterday_len = daylen