Answer

In Jain tradition, Posh Dashmi Atham is observed during the Posh Dashmi festival, which is connected with devotion to Bhagwan Parshvanath, the 23rd Tirthankar.

For 2027, the exact English calendar dates depend on the Jain lunar calendar, local sunrise, tithi timing, and location.

Sorry, I can only provide information that is clearly established within Jain tradition.

Explanation

“Atham” usually refers to an 8-day observance/tapasya, and “Posh Dashmi” refers to the sacred Dashmi tithi in the month of Posh.

To know the exact 2027 dates, please check a trusted Jain Panchang for your city or local Jain sangh calendar.

Takeaway

For vows, fasting, or Atham, it is best to follow the local Jain Panchang and guidance of your Guru Bhagwant or Jain sangh, because tithi observance can vary by location.