Calculate from datetime ot JDN

utils.py

def dt_to_jdn(dt):
    """Convert datetime to Julian Day Number

    .. warning: Please verify this calculating method

    This convertion is based on:

    'Practical Astronomy with your Calculator or Spreadsheet',
        4th ed., Duffet-Smith and Zwart, 2011.

    https://en.wikipedia.org/wiki/Julian_day


    :param dt: datetime to convert. This must be on UTC.
    :type dt: datetime.datetime
    :return: Julian Date

    :Examples:

    .. code-block:: console

       import datetime
       from utils import *
       dt_to_jdn(datetime.datetime.now())
       2458352.5651478795
    """

    year = dt.year
    month = dt.month
    day = dt.day

    hours = dt.hour
    min = dt.minute
    sec = dt.second
    micro = dt.microsecond

    if month == 1 or month == 2:
        year_ = year - 1
        month_ = month + 12

    else:
        year_ = year
        month_ = month

    if dt > datetime.datetime(1582, 10, 15):
        A = math.trunc(year_/100)
        B = 2 - A + math.trunc(A/4)
    else:
        B = 0

    if year_ < 0:
        C = math.trunc((365.25 * year_) - 0.75)
    else:
        C = math.trunc(365.25 * year_)

    D = math.trunc(30.6001 * (month_ + 1))

    JD = B + C + D + day + 1720994.5

    decimal_part = ((hours - 12)/24.) + ((min)/1440.) + ((sec)/86400.) + ((micro)/8.64e10)
    JDN = JD + decimal_part
    return JDN