Code to get tamil months/date from english months

Tamil Month Calculator - Simpler.py

# -*- coding: utf-8 -*-
"""Tamil Month Calculator - Simpler.ipynb

Automatically generated by Colaboratory.

Original file is located at
    https://colab.research.google.com/drive/1vYnNRVuCUZa-n1V6P18FUcONYflxJdcd
    
Created by Ravi Annasamy - ravi.annaswamy@gmail.com

Detailed discussuion is here - https://groups.google.com/g/mintamil/c/DSXP2KHvgRw
"""

import datetime as dtm
import math

month_names = 'Chiththirai,Vaigaasi,Aani,Aadi,Aavani,Purattaasi,Aippasi,Kaarthigai,Margazhi,Thai,Maasi,Panguni'.split(',')
assert len(month_names)==12


def _fract(x):
    return x - int(x)


def cd_to_jd(gdate):
    """Convert Greenwich date to Julian date."""
    result = 1721424.5 + gdate.toordinal()
    try:
        return result + (gdate.hour * 3600 + gdate.minute * 60 +
                         gdate.second + gdate.microsecond * 1e-6) / 86400.0
    except AttributeError:
        # date parameter is of type 'date' instead of 'datetime'
        return result


def jd_to_cd(jd):
    """Convert Julian date to calendar date."""
    date = jd - 1721424.5
    result = dtm.datetime.fromordinal(int(date))
    result += dtm.timedelta(seconds=86400.0 * _fract(date))
    return result


def start_of_day(gdatetime):
    """Set the time part of a datetime value to zero."""
    return gdatetime.replace(hour=0, minute=0, second=0, microsecond=0)


def solar_hours(t):
    """Convert siderial hours into solar (normal) hours."""
    return t * 0.9972695663


def eccentric_anomaly(am, ec):
    """Return eccentric anomaly for given mean anomaly and eccentricity.

    am: mean anomaly
    ec: eccentricity,
    """
    m = am % (2 * math.pi)
    ae = m
    while 1:
        d = ae - (ec * math.sin(ae)) - m
        if abs(d) < 0.000001:
            break
        ae -= d / (1.0 - (ec * math.cos(ae)))
    return ae


def true_anomaly(am, ec):
    """Return true anomaly for given mean anomaly and eccentricity.

    am: mean anomaly
    ec: eccentricity,
    """
    ae = eccentric_anomaly(am, ec)
    return 2.0 * math.atan(math.sqrt((1.0 + ec) / (1.0 - ec)) * math.tan(ae * 0.5))

  
def get_ayan(year, month, day):
    a = 16.90709 * year/1000 - 0.757371 * year/1000 * year/1000 - 6.92416100010001000
    b = (month-1 + day/30) * 1.1574074/1000
    return -(a+b)

def sun_long(gdate, zone):
    """Return sun longitude in degrees for given Greenwich datetime (UTC)."""

    t = (cd_to_jd(gdate) - 2415020.0 + zone/24.0) / 36525.0
    t2 = t * t

    l = 279.69668 + 0.0003025 * t2 + 360.0 * _fract(100.0021359 * t)
    m1 = 358.47583 - (0.00015 + 0.0000033 * t) * t2 + 360.0 * _fract(99.99736042 * t)
    ec = 0.01675104 - 0.0000418 * t - 0.000000126 * t2

    # sun anomaly
    at = true_anomaly(math.radians(m1), ec)

    a1 = math.radians(153.23 + 360.0 * _fract(62.55209472 * t))
    b1 = math.radians(216.57 + 360.0 * _fract(125.1041894 * t))
    c1 = math.radians(312.69 + 360.0 * _fract(91.56766028 * t))
    d1 = math.radians(350.74 - 0.00144 * t2 + 360.0 * _fract(1236.853095 * t))
    e1 = math.radians(231.19 + 20.2 * t)
    h1 = math.radians(353.4 + 360.0 * _fract(183.1353208 * t))

    d2 = (0.00134 * math.cos(a1) + 0.00154 * math.cos(b1) + 0.002 * math.cos(c1) +
          0.00179 * math.sin(d1) + 0.00178 * math.sin(e1))

    sr = (at + math.radians(l - m1 + d2)) % (2 * math.pi)
    return math.degrees(sr)
  
def sun_long_precessed(gdate, zone):
    t = (cd_to_jd(gdate) - 2415020.0 + zone/24.0) / 36525.0
    sr = sun_long(gdate, zone)
    ay = get_ayan(gdate.year, gdate.month, gdate.day+gdate.hour/24.0)
    return sr+ay

dt = dtm.datetime(2001,3,14,18,0)
zone=-5.5
assert sun_long_precessed(dt,zone)==330.12115511267547

dt = dtm.datetime(2019, 5, 16, 18, 0)
zone=-5.5
print(dt, sun_long_precessed(dt,zone))

def print_month_firstdays(year_requested):
  zone = -5.5
  year = year_requested
  mon,day,hour,minute = 3, 31, 18, 0

  date = dtm.datetime(year, mon, day, hour, minute)
  print(date)


  last=12
  
  daycount=0
  search=True
  for _ in range(400):
    sunlong = sun_long_precessed(date, zone)
    house = int(sunlong)%360.*60.
    if house<0:
      house+=21600
    house=int(house/1800.)+1
    deg=(sunlong)%30
    if deg<1 and house!=last:
      if search:
        search=False
      else:
         if house==1: 
          print(12, daycount)
         else:
          print(house-1, daycount)
      last=house

      print(str(date.year)+'/'+str(date.month)+'/'+str(date.day),':',month_names[house-1], '1')
      daycount=0
    date=date+dtm.timedelta(days=1)
    daycount+=1

print_month_firstdays(2019)

def print_daily_calendar(year_requested):
  zone = -5.5
  year = year_requested
  mon,day,hour,minute = 3, 31, 18, 0

  date = dtm.datetime(year, mon, day, hour, minute)
  print('Search started on: ', date)


  last=12
  
  daycount=0
  search=True
  for _ in range(400):
    sunlong = sun_long_precessed(date, zone)
    house = int(sunlong)%360.*60.
    if house<0:
      house+=21600
    house=int(house/1800.)+1
    deg=(sunlong)%30
    if deg<1 and house!=last:
      if search:
        search=False
      else:
         if house==1: 
          print(12, daycount)
         else:
          print(house-1, daycount)
      last=house
      print()
      #print(str(date.year)+'/'+str(date.month)+'/'+str(date.day),':',month_names[house-1], '1')
      daycount=0
    if not search:
      print(str(date.year)+'/'+str(date.month)+'/'+str(date.day),':',month_names[house-1], daycount+1)
    date=date+dtm.timedelta(days=1)
    
    daycount+=1

print_daily_calendar(2019)

year,mon,day,hour,minute=2000,1,1,0,0
assert sun_long(dtm.datetime(year, mon, day, hour, minute),0)==279.86755582331756

year,mon,day,hour,minute=1996,8,25,0,0
assert sun_long(dtm.datetime(year, mon, day, hour, minute),0)==152.07711722719677

def get_tamil_date(year,mon,day):
  hour,minute=18,10
  zone=-5.5
  dt=dtm.datetime(year,mon,day,hour,minute)
  sr=sun_long_precessed(dt,zone)
  print(month_names[int(sr/30)])
  daycount=1
  while True:
    if sr%30<1 and sr%30>0:
      break
    dt = dt - dtm.timedelta(days=1)
    sr=sun_long_precessed(dt,zone)
    daycount+=1
  print(daycount)

year,mon,day=2019,6,15
get_tamil_date(year,mon,day)

year,mon,day=2015,7,27
get_tamil_date(year,mon,day)

year,mon,day=1950,1,26
get_tamil_date(year,mon,day)

year,mon,day=2022,6,1
get_tamil_date(year,mon,day)