In Jainism, Ashtami (Aatham) – the 8th day of each lunar fortnight – is a very important tithi for spiritual practice.

1. Ashtami as one of the “5 Tithi”

Ashtami is counted in the special pañch tithi (5 holy days) of every fortnight:

• 4th (Chauth)
• 8th (Ashtami / Aatham)
• 14th (Chaturdashi)
• Poonam (Full moon)
• Amavasya (New moon)

On these days, any dharma–kriyā (religious activity) is believed to give stronger punya (merit) than on ordinary days – e.g.:

• Upvās (fast), ekāsan, biyāsan, ayambil
• Pratikraman, samayik, meditation
• Svaadhyāy (scripture study), listening to pravachan
• Daan (charity), Jina-pūjā

You can read more about the 5 tithis here

2. Fasting and special tapas on Ashtami

Many Jains keep:

• Upvās or Ayambil on every (or selected) Ashtami
• Longer fasts like Attham (3-day continuous fast) that traditionally end on Ashtami

This is done for:

• Saṃvar – stopping new karmas
• Nirjarā – shedding old karmas
• Increasing inner control and reducing attachment

Simple explanation of “Aatham” is given here

3. Paushadh on Ashtami

A very praised practice is Paushadh – living like a sadhu/sadhvi for the whole day (or part of the day):

• Staying separate from household work
• Following more vows, silence, study, pratikraman

Traditionally, Paushadh is often done on Ashtami and Chaturdashi. More on Paushadh:

4. Food discipline (no green vegetables on Ashtami)

In many Śvetāmbara traditions, on Ashtami people:

• Avoid green leafy vegetables, sometimes more items

Reason: on these tithis, life in plants and small organisms is considered more active, so plucking/eating them causes comparatively more hiṃsā. So, this rule helps to reduce violence and increase ahimsā-bhāv. Explanation here

5. Digambar / Shwetambar view

• Both traditions regard Ashtami as an auspicious day for tapas and dharma.
• Exact rules (what to eat, how to fast, details of Paushadh) can differ by sect and local maryādā, but the core spirit is the same:

- Use Ashtami for more sādhanā, less worldly activity.

6. Essence of Ashtami in Jain life

• A gentle reminder, twice every month, to:

- Slow down worldly work - Do extra prayer, pratikraman, fasting, study - Strengthen ahimsā, aparigraha and inner purity

So, the importance of Ashtami in Jainism is that it is a regular, powerful spiritual checkpoint in the month, designed to help the soul move a little closer to moksha.