In the Shwetambar Jain tradition, “tithi” means a lunar date. Many households take pachchakkhān (a vow) to follow certain food-discipline on specific tithis.

• 1 tithi: You observe on only one key tithi in each fortnight, usually Chaudas (14th). So you avoid green vegetables (and follow stricter ahiṁsā rules) on every Sud 14 and Vad 14.

• 2 tithi: You observe on two key tithis in each fortnight—Aatham (8th) and Chaudas (14th). So you avoid green vegetables on every Sud 8, Sud 14, Vad 8, and Vad 14.

Notes

• “Sud” = Shukla paksha (bright half). “Vad” = Krishna paksha (dark half).
• Many families extend this to 3, 4, or 5 tithis by adding Poonam (full moon), Amas (new moon), and Choth (4th), but 1 tithi and 2 tithi commonly mean the above in Shwetambar practice.

For a simple explanation of why Jains avoid green vegetables on these tithis and what “5 tithi” means, see: