Answer

For 2027, Posh Vad Dasam is on:

Sunday, January 31, 2027

So the correct date is Jan 31, not Jan 2.

Explanation

The confusion happens because:

• Jan 2, 2027 falls in the previous lunar month cycle — it is Magshar Vad Dasam in Gujarati/Jain calendar context.
• Jan 31, 2027 is Posh Vad Dasam.

Takeaway

If you are observing any Jain tithi connected specifically with Posh Vad Dasam, then for 2027 you should consider:

January 31, 2027 — Sunday