Answer

In Jain tradition, 2 upvas is called Chhath / Chhatt because it is counted according to the number of meal-times skipped, not simply by the number of calendar days.

Explanation

Traditionally, a day has two main eating times:

• Morning / daytime meal
• Evening meal

For 2 upvas, a person does not eat for two full days. Along with the meals before and after the fast being regulated, the count becomes connected with six meal-times. Therefore, it is called Chhath, meaning “sixth.”

Similarly:

• 1 upvas is called Chauvihar upvas or sometimes linked with skipping multiple meal-times
• 2 upvas is called Chhath
• 3 upvas is called Attham

Spiritual Understanding

The name reminds us that tapasya is not only about counting days, but about disciplined control over food, senses, and desires. In Jain Dharma, upvas means staying closer to the soul by reducing attachment to the body and food.

Takeaway

2 upvas is called Chhath because the traditional counting is based on six meal-times connected with the fast.