Answer

In the Jain calendar, a tithi is a lunar day.

The difference between 1 tithi and 2 tithi is simply their position in the lunar fortnight:

• 1 tithi means the first lunar day.
• 2 tithi means the second lunar day.

Explanation

A Jain lunar month is divided into two halves:

• Sud / Shukla Paksha — the bright half, from new moon toward full moon
• Vad / Krishna Paksha — the dark half, from full moon toward new moon

Each half has tithis numbered from 1 to 15.

So:

• Sud 1 is the first tithi of the bright half.
• Sud 2 is the second tithi of the bright half.
• Vad 1 is the first tithi of the dark half.
• Vad 2 is the second tithi of the dark half.

Spiritual Understanding

In Jain Dharma, certain tithis are especially important for religious practices such as uposath, pratikraman, ayambil, fasting, chaudas, punam, amavasya, and festival observances.

The number of the tithi helps decide which religious observance is performed on that lunar day.

Takeaway

1 tithi is the first lunar day, and 2 tithi is the second lunar day. Their religious significance depends on whether they fall in Sud or Vad and on the specific Jain observance connected with that date.