Michami Dukadum (Michchhami Dukkadam) is a Jain confession/forgiveness gesture. Here’s when to say it:

• Main time: On Samvatsari, the last day of Paryushan, to seek forgiveness from all living beings for any harm caused in thought, speech, or action during the year.
• Also during Paryushan: On other days of the festival, and at the end of it, many laypeople and monks/nuns say it to extend and receive forgiveness.
• Anytime you feel you may have harmed someone: If you regret a hurtful thought, word, or deed, you can say Michchhami Dukkadam to the person(s) you affected.
• Across communities: It is usually addressed to all beings you think you may have harmed, spoken to, or failed in some duty toward, not just friends or family.
• Digambar vs. Shwetambar nuance: Both traditions use Michchhami Dukkadam, but the exact phrases and customs may vary by local temple traditions. The essential idea—seeking forgiveness and sparing conflict—remains the same.

In short: say it on Samvatsari (and during Paryushan) to everyone you’ve interacted with over the year, and at any time you want to repair a hurt by asking for forgiveness.