Answer

The difference in tithis between Deravasi and Sthanakvasi Jains usually comes from calendar tradition and tithi calculation, not from a difference in core Jain Dharma.

Explanation

A tithi is a lunar day. In Jain practice, religious observances are often based on the moon calendar, not the fixed English calendar.

Because of this:

• A tithi may start or end at different times on the same civil day.
• Sometimes a tithi is kshaya meaning it gets skipped.
• Sometimes a tithi is vriddhi meaning it repeats.
• Different Jain communities may follow slightly different panchangs or rules for deciding which civil day to observe a vrat, festival, or religious event.

So:

• Deravasis may observe according to one traditional panchang system.
• Sthanakvasis may follow another accepted calculation or local tradition.

That is why the same Jain festival or fast can appear on different dates for the two communities.

Spiritual Understanding

In Jain Dharma, the main purpose is not to argue about the date, but to preserve:

• bhakti
• discipline
• samyak charitra
• shraddha in vrat and niyam

The outer date may differ, but the inner aim remains the same: purification of the soul.

Takeaway

So, the difference in tithis is mainly due to lunar calendar interpretation, not a difference in fundamental Jain principles. The spiritual essence of the observance remains unchanged.