Nutze Skyfield fuer praezisere Daemmerungsberechnung

public/py/vendor/jplephem/calendar.py

@@ -0,0 +1,35 @@
+"""Routines for dealing with Julian dates."""
+
+def compute_calendar_date(jd_integer, julian_before=None):
+    """Convert Julian day ``jd_integer`` to ``(year, month, day)``.
+
+    Uses the proleptic Gregorian calendar unless ``julian_before`` is
+    set to a specific Julian day, in which case the Julian calendar is
+    used for dates older than that.
+
+    """
+    use_gregorian = (julian_before is None) or (jd_integer >= julian_before)
+
+    # See the Explanatory Supplement to the Astronomical Almanac 15.11.
+    f = jd_integer + 1401
+    f += use_gregorian * ((4 * jd_integer + 274277) // 146097 * 3 // 4 - 38)
+    e = 4 * f + 3
+    g = e % 1461 // 4
+    h = 5 * g + 2
+    day = h % 153 // 5 + 1
+    month = (h // 153 + 2) % 12 + 1
+    year = e // 1461 - 4716 + (12 + 2 - month) // 12
+    return year, month, day
+
+def compute_julian_date(year, month=1, day=1.0):
+    """Given a proleptic Gregorian date, return a Julian date float."""
+    return compute_julian_day(year, month, day) - 0.5
+
+def compute_julian_day(year, month=1, day=1):
+    """Given a proleptic Gregorian date, return a Julian day int."""
+    janfeb = month < 3
+    return (+ 1461 * (year + 4800 - janfeb) // 4
+            + 367 * (month - 2 + janfeb * 12) // 12
+            - 3 * ((year + 4900 - janfeb) // 100) // 4
+            - 32075
+            + day)