The Chedi calendar is the oldest known Indian calendar, dating back to the 10th century BCE.

The Saka calendar is based on the tropical year, which is the time it takes for the Earth to complete one orbit around the Sun.

The Vikram Samvat calendar begins in 57 BCE, which is believed to be the year of King Vikramaditya's coronation.

The Saka calendar is a solar calendar, which means that it is based on the Earth's orbit around the Sun.

The Vikram Samvat calendar is a lunisolar calendar, which means that it is based on both the Earth's orbit around the Sun and the Moon's orbit around the Earth.

The Kollam Era is a solar calendar, which means that it is based on the Earth's orbit around the Sun.

The Chedi calendar is a lunisolar calendar, which means that it is based on both the Earth's orbit around the Sun and the Moon's orbit around the Earth.

The Saka calendar is the national calendar of India.

The Kollam Era is the official calendar of the state of Kerala.

The Kollam Era is the official calendar of the state of Tamil Nadu.

The Saka calendar is the official calendar of the state of Andhra Pradesh.

The Saka calendar is the official calendar of the state of Telangana.

The Saka calendar is the official calendar of the state of Karnataka.

The Saka calendar is the official calendar of the state of Maharashtra.

The Saka calendar is the official calendar of the state of Gujarat.