docs/library: add new module suntime

Signed-off-by: Lorenzo Cappelletti <lorenzo.cappelletti@gmail.com>

docs/library/index.rst

@@ -70,6 +70,7 @@ library.
    socket.rst
    ssl.rst
    struct.rst
+   suntime.rst
    sys.rst
    time.rst
    uasyncio.rst

docs/library/suntime.rst

@@ -0,0 +1,94 @@
+:mod:`suntime` -- sunrise and sunset time
+
+.. module:: suntime
+      :synopsis: sunrise and sunset time
+
+Approximated calculation of sunrise and sunset time. Adapted from
+https://github.com/SatAgro/suntime.
+
+
+Class methods
+-------------
+
+.. class:: Sun(latitude, longitude)
+
+   Arguments *latitude* and *longitude* are floats representing the
+   coordinates of a place on Earth.
+
+
+.. method:: get_sunrise_time(year, month, day)
+
+   Calculate the sunrise time for the given date. It returns a tuple of
+   integers ``(hour, minute)`` in UTC time or ``None`` if sun doesn't
+   raise on that location at the given date.
+
+
+.. method:: get_sunset_time(year, month, day)
+
+   Calculate the sunset time for the given date. It returns a tuple of
+   integers ``(hour, minute)`` in UTC time or ``None`` if sun doesn't
+   set on that location at the given date.
+
+
+Examples of usage
+-----------------
+
+This example calculates sunrise and sunset of three major cities::
+
+    import suntime
+
+    test('suntime: example')
+
+    Rome     = suntime.Sun( 41.902782 , 12.496366 )
+    Warsaw   = suntime.Sun( 51.21     , 21.01     )
+    CapeTown = suntime.Sun(-33.9252192, 18.4240762)
+
+    dt1 = (2000, 1, 1)
+    sr1 = Rome.get_sunrise_time(*dt1) # (6, 38)
+    ss1 = Rome.get_sunset_time (*dt1) # (15, 49)
+    print('Rome:', sr1, ss1)
+
+    dt2 = (2014, 10, 3)
+    sr2 = Warsaw.get_sunrise_time(*dt2) # (4, 39)
+    ss2 = Warsaw.get_sunset_time (*dt2) # (16, 10)
+    print('Warsaw:', sr2, ss2)
+
+    dt3 = (2016, 12, 21)
+    sr3 = CapeTown.get_sunrise_time(*dt3) # (3, 32)
+    ss3 = CapeTown.get_sunset_time (*dt3) # (17, 57)
+    print('Cape Town:', sr3, ss3)
+
+If :mod:`datetime` module is available, results above can be expressed
+in local time::
+
+    import datetime as datetimelib
+
+    timedelta = datetimelib.timedelta
+    timezone  = datetimelib.timezone
+    datetime  = datetimelib.datetime
+
+    utc = timezone.utc
+    tz1 = timezone(timedelta(hours=1))
+    tz2 = timezone(timedelta(hours=3))
+    tz3 = timezone(timedelta(hours=2))
+
+    # https://www.timeanddate.com/sun/italy/rome?month=1&year=2000
+    print('Rome:')
+    rt1 = datetime(*dt1, *sr1, tzinfo=utc).astimezone(tz1) # 2000-01-01 07:38:00+01:00
+    st1 = datetime(*dt1, *ss1, tzinfo=utc).astimezone(tz1) # 2000-01-01 16:49:00+01:00
+    print('>', rt1)
+    print('>', st1)
+
+    # https://www.timeanddate.com/sun/poland/warsaw?month=10&year=2014
+    print('Warsaw:')
+    rt2 = datetime(*dt2, *sr2, tzinfo=utc).astimezone(tz2) # 2014-10-03 07:39:00+03:00
+    st2 = datetime(*dt2, *ss2, tzinfo=utc).astimezone(tz2) # 2014-10-03 19:10:00+03:00
+    print('>', rt2)
+    print('>', st2)
+
+    # https://www.timeanddate.com/sun/south-africa/cape-town?month=12&year=2016
+    print('Cape Town:')
+    rt3 = datetime(*dt3, *sr3, tzinfo=utc).astimezone(tz3) # 2016-12-21 05:32:00+02:00
+    st3 = datetime(*dt3, *ss3, tzinfo=utc).astimezone(tz3) # 2016-12-21 19:57:00+02:00
+    print('>', rt3)
+    print('>', st3)