In Jainism, scriptures do NOT fix any “one Tirthankar = one weekday” rule. You can worship any Tirthankar on any day.

However, in many Jain families a popular (non‑scriptural) practice is to remember the first 7 Tirthankars on the 7 days of the week like this:

1. Sunday (Ravivaar) – Bhagwan Rishabhdev / Adinath (1st Tirthankar)
2. Monday (Somvaar) – Bhagwan Ajitnath (2nd)
3. Tuesday (Mangalvaar) – Bhagwan Sambhavnath (3rd)
4. Wednesday (Budhvaar) – Bhagwan Abhinandan Swami (4th)
5. Thursday (Guruvaar) – Bhagwan Sumatinath (5th)
6. Friday (Shukravaar) – Bhagwan Padmaprabhu (6th)
7. Saturday (Shanivaar) – Bhagwan Suparshvanath (7th)

Points to remember:

• This is a devotional / regional tradition, not an Agamic rule.
• Both Digambar and Shvetambar accept worship of all 24 Tirthankars every day; this weekday assignment is just for ease of remembrance and bhakti.
• Many Jains simply do Chauvvisi (worship of all 24 Tirthankars) daily, without tying them to specific weekdays.

You can read a simple explanation of this practice here