Answer

Siddhi Tap does not have one fixed universal start date. Jain sources describe it as one of the Jain austerities, and Jain religious dates are generally based on the lunar calendar, so they can vary by year and by tradition. ( jainelibrary.org)

Explanation

In practice, Siddhi Tap usually starts on the day a devotee takes the vow, as तय किया जाता है by the local Jain sangh, guru, or panchang. So the exact start depends on the city, sect, and the specific tapasya program. This is why there is no single all-India start date for Siddhi Tap. ( jainelibrary.org)

Spiritual Understanding

In Jain Dharma, the value is in the bhav, niyam, and samarpan behind the tap. The timing matters less than taking it with sincerity, discipline, and proper guidance. ( jainelibrary.org)

Takeaway

So, Siddhi Tap starts when your tapasya vow begins, not on one fixed calendar day. For an exact date, it must be checked in the relevant local Jain panchang or sangh schedule. ( jainworld.jainworld.com)