Panchanga is the astrological almanac based on the ancient Vedic system of calculation. It is known as Panchanga or ‘Five Limbs’ in Sanskrit as it considers five aspects of time: tithi(day of the lunar cycle), vara(week), nakshatra(star), yoga(quality of time) and karana(time appropriate for certain type of actions), based on the movements of the Moon. There are many types of panchangas. The one most often consulted clumps time into a 60 year cycle or samvatsara – with each year assigned a special name, for instance, this year is known as Nandana Samvatsara.
A year is typically divided into two parts: Uttarayana (When the Sun enters the Tropic of Capricorn) and Dakshinayana (When the Sun enters the Tropic of Cancer). During Uttarayana we have longer days and during Dakshinayana we have longer nights.
The year is further subdivided into Ritus or Seasons. Each Ritu falls over a period of two months. Furthermore, each month is categorized into two pakshas: Krishna Paksha and Shukla Paksha and each Paksha is made up of 15 days. Each day is called a Tithi eg.Prathama(first), Dwitiya(second), etc up to Purnima or Amavasya.
The transit of the moon in a particular constellation on a particular day or tithi is considered as the Nakshatra. We have 27 constellations in 12 zodiac signs. Each zodiac sign is divided by 30 degrees, so totally 360 degrees are there.