Panchang
Hindu calendar is lunar based, i.e, it depends on the phases of the moon. In it, the day starts with local sunrise. It is allotted five "properties", called angas. They are:
  • Tithi (one of 30 divisions of a synodic month) active at sunrise
  • Vaasara, vaar (ravi-vaar, som-vaar, etc.) or weekday
  • Nakshatra (one of 27 divisions of the celestial ecliptic) in which the moon resides at sunrise
  • Yoga (one of 27 divisions based on the ecliptic longitude of the sun and moon) active at sunrise
  • Karana (divisions based on tithis) active at sunrise.
Together these are called the panchangas.

Rashi

It is the one of the 12 zodiac constellation. All the objects of the solar system pass through these. There are twelve rashi names, there are twelve lunar month names. When the sun transits into the Mesha rashi in a lunar month, then the name of the lunar month is Chaitra. When the sun transits into Vrishabha, then the lunar month is Vaishakh. So on.
  • Mesh
  • Vrishabha
  • Mithuna
  • Kark
  • Simha
  • Kanya
  • Tula
  • Vrishchika
  • Dhanu
  • Makar
  • Kumbha
  • Meen

Tithi

A lunar day. Named in sanskrit, amavasya and purnima and prathama, dvitiya, etc . As tithi changes the phase of the moon also changes
Paksha: A lunar month is divided in two pakshas. Shukla paksha size of moon increases. Tithi changes from Amavasya to Purnima. Waxing phase. Krishna paksha size of the moon decreases. Tithi goes from Purnima to Amavasya. Waning Phase.

Months

  • Chaitra
  • Vaisakha
  • Jyaishtha
  • Ashadha
  • Sravana
  • Bhadrapada
  • Asvina
  • Kartika
  • Margasirsha
  • Pausha
  • Magha
  • Phalguna

Vaar

  • Ravivara
  • Somavara
  • Mangalavara
  • Buddhavara
  • Brihaspativara
  • Shukravara
  • Shanivara

Nakshatra

  • Aswini
  • Bharani
  • Kritika
  • Rohini
  • Mrigashirsha
  • Ardra
  • Punarvasu
  • Pushya
  • Ashlesha
  • Magha
  • Poorvaphalguni
  • Uttaraphalguni
  • Hasta
  • Chitra
  • Swati
  • Vishakha
  • Anuradha
  • Jyeshta
  • Moola
  • Poorvashadha
  • Uttarashadha
  • Shravana
  • Dhanishta
  • Satabisha
  • Poorvabhadrapada
  • Uttarabhadrapada
  • Revati

Yoga

  • Vishkambha
  • Priti
  • Ayushman
  • Saubhagya
  • Sobhana
  • Atiganda
  • Sukarma
  • Dhriti
  • Soola
  • Ganda
  • Vriddha
  • Dhruva
  • Vyagatha
  • Harshana
  • Vajra
  • Siddhi
  • Vyatapata
  • Variyan
  • Parigha
  • Siva
  • Siddha
  • Sadhya
  • Subha
  • Shukla
  • Brahma
  • Indra
  • Vaidhriti

Karana

  • Kinstughna
  • Bhava
  • Balava
  • Kaulava
  • Taitula
  • Garaja
  • Vanija
  • Visti (Bhadra)
  • Sakuni
  • Chatuspada
  • Nagava
Calendar Types
There are many types of calendars used in India. Mostly they follow Lunar Calendar. Although there are some who follow Luni-Solar System. An attempt to cover a large portion of those has been made, and will continue.

Year Types

There are several types of year numbering systems. Three of those implemented are :
  • Vikram Samvat -(New Year from Chaitra).
  • Vikarm Samvat (Kartak) - (New Year from Kartik). Used in Gujarat and other places, new year just after diwali.
  • Saka - Indian National Calendar.

Month Types

There are two types of calendars. Amavasyant and Purnimant. All other things remain the same in these two, only the month change is on amavasya and purnima respectively. This map gives a rough idea of the types of calendars used in India. This information was collected from the internet. If you have any corrections please contact me.
Location

As the panchang of the day is defined at the sunrise. The location plays a very important role. The latitude, longitude and the timezone of a place determine the time of the sunrise and sunset. For most of India the location of Ujjain can be considered as a crude approximation. For other countries the changes in panchang would be significant. The same principle used in India can be used to find panchang for any location on the earth.

Note: That exact moon phase and astronomical events and transitions would happen for all locations simultaneously. But the timezone and longitude differences ensure that time shown on clocks differ, also their positions in the sky may also differ.

Sunrise Sunset Timings

Depending on the location and timezone of a place the sunrise and sunset of a place can be calculated. The sunrise is defined to take place when the upper edge of sun rises from the horizon, similarly for sunset is defined when the trailing edge of the sun's disk disappears. Atmospheric Refraction is also taken into account as at rise/set the actual position of sun is slightly different from apparent position.

But in Hindu Calendar the sunrise/sunset is taken to be the point when the middle of the disk of the sun crosses the horizon. The time difference due to this can be a couple of minutes. This affects the Jyotish, muhurtum calculations. This app implements the latter version, i.e, according to Hindu convention.

Ayanamsa

It is the amount of precession, or the longitudinal difference between the Tropical (Sayana) and Sidereal (Nirayana) zodiacs. Because of precession of earth (which causes the pole star to change too) there is inconsistency in the star charts used in the past and the present. To compensate, this quantity is added to longitudes to find values coherent with the past. The default in this application is Lahiri/ Chitrapaksha Ayanamsa. But you can choose Raman and Krishnamurti (Old) too from settings.

Rahu and Ketu

Rahu and Ketu were Asuras in Hindu Mythology responsible for eclipses of sun and moon. They do cause eclipse, but in reality they are not asuras. They are actually two points of intersection of the paths of the Sun and the Moon as they move around the celestial sphere. (Ascending and descending nodes on the lunar orbit). When the position of moon on Amavasya or Purnima falls near Rahu or Ketu's Position, we have an eclipse (partial or complete). They are imaginary, i.e, they have a position in sky but there is nothing present there.

Kundali

Kundali is a pictorial representation of the position of the planets (Grahas) in the 12 rashis. In the northern style Kundali, the Lagna (Ascendant Rising Rashi) takes the centeral position. The rest are numbered in anti-clockwise order. In Southern type of Kundali the position of the rashis is fixed. The second one on the first row is Mesha(Aries). The others are numbered in clockwise order. The rashi of the Lagna is depicted as a cross line on its box.

Jyotish Terms

Rahu Kalam, Yama Ghanta, Guli Kalam, Abhijit and Dur Muhurt are some of the 'kal' and 'muhurt'. The day from sunrise to sunset, and the night from sunset to the next sunrise, is divided into different divisions. And based on the day of the week and/or other factors, rules define their duration and time of occurance.

Choghadiya

The daytime and night time is divided into 8 divisions each. Thus giving day and night choghadiya. These divisions are assigned any one of these names based on rules and are presented in a tabular form.

  • Amrut, Shubh and Labh are considered the Best Choghadiya's
  • Chal is considered as Good Choghadiya
  • Udyog, Kal and Rog are considered inauspicious

Hora

Similarly for Hora tables 12 divisions each are made for the day and night duration and are named after planets

Lagna

Lagna is zodiac sign near the horizon at the point of sunrise.

Hindu Time

  • Ghati, Pal ( Vighati, Kala) and Vipal (Lipta, Vikala) are Hindu Units of Time
  • They are similar to Hour: Minute : Seconds and are also called Ishta Kaal
  • Hindu Day starts at sunrise instead of 12:00 in the night
  • A day is divided into 60 Ghatis, each ghati 24 minutes long
  • A ghati has 60 pal and a pal has 60 vipala
  • Two ghatis make a Muhurta

Match Making

Kundali Milan or Ashta Koota Milan is done by comparing the kundali of bride and groom on a 36 point scale. There are eight different criteria on which the calculation is done.

  • Varn
  • Vashya
  • Tara
  • Yoni
  • Grah Maitri
  • Gana
  • Bhakoot
  • Nadi
These criteria have 1, 2, 3. ... upto 8 points respectively. Each one of them is supposed to be responsible for different aspect of marriage.