In Jainism, Ekasana is a practice of eating only once a day, and it is a significant form of self-discipline (tapasyā or austerity). The commitment to do ekasana for 5 years is a notable vrata (vow) and is often undertaken for spiritual upliftment.

Regarding your question:

1. When should one start the Ekasana procedure for 5 years?

There is no fixed date prescribed in Jain scriptures for starting ekasana for such a long duration. However, traditionally, many people choose to start such vows on auspicious days, such as:

• Paryushan Parva: Beginning or end of the holy festival.
• Agnivasa or Samvatsari: The day of forgiveness.
• Akshaya Tritiya, Kartik Shukla Pratipada, Mahavir Jayanti, or other Jain festivals.
• Panchami: As you mentioned, some Jains observe special austerities on every Panchami (5th day of the lunar fortnight).

It is most important to discuss with a Jain monk (Sadhu/Sadhvi) or a learned scholar (Panditji) before taking such a long-term vow, as they can guide you on the proper sankalp (declaration), auspicious timings, and how to observe the vow according to your sect's traditions (Sthanakvasi, Terapanthi, Murtipujak, etc.).

2. Ekasana on Pancham (Panchami) Each Day for 5 Years

If you wish to perform ekasana only on every Panchami (the 5th day of each lunar fortnight) for 5 years, you would:

• Do ekasana on every Panchami tithi, i.e., twice a month.
• Continue this practice for 5 years.

Again, there is no fixed universal starting date, but it is considered auspicious to begin on a Panchami itself or any spiritually significant day. You should formally declare your intent (sankalp) in the presence of a guru or at least with a mental prayer to the Tirthankaras.

Summary

• There is no single “correct” date; auspicious Jain days are preferred.
• Take the vow (sankalp) in front of a guru or with devotion and clarity of intention.
• The vow can be started on a Panchami, during Paryushan, or another holy day.
• Consult with a local Jain Acharya, monk, or Pandit for personalized guidance and for the specific procedure according to your tradition.

May your tapasya be fruitful and lead to spiritual progress.

If you have a specific sect or tradition in mind, or need a sankalp mantra or formal procedure, please mention it for more detailed guidance.