This depends on your lineage.
Pambu Panchangam typically uses Chennai (Madras) sunrise. If you live in a different time zone (e.g., USA, UK, Singapore), you must apply a correction. Use an online desaantara correction tool. pambu panchangam 2021-22 pdf
Since "Pambu Panchangam" (also known as the "Snake Panchangam" or Dr. S. P. S. Ramanujam Iyengar's Panchangam) is a highly specific Tamil astrological almanac, the content below highlights its unique features and provides download/study guidance. This depends on your lineage