Dhanya Teras (also called Dhan Teras) is the 13th lunar day (terā) of the Krishna Paksha in Kartik. In Jainism it is especially connected with Lord Mahavira’s spiritual journey toward Moksha.

• What it marks: It is remembered as the day Mahavira began his Yoga-nirodha (meditation/concentration) which led toward liberation. In some accounts this day is followed by the events of his Nirvana a few days later.
• Traditions: Both Śvetāmbara and Digambara communities observe Dhanya Teras, with the emphasis being on Mahavira’s vow-filled preparation and the auspiciousness of this tithi. The core meaning is the blessing of spiritual wealth (moksha) that Mahavira’s effort represents, rather than material wealth.

In short: Dhanya Teras is celebrated as the blessed 13th day marking Mahavira’s entry into deep meditation on the path to Nirvana/Moksha.