The lunar day follows the published Thai calendar, anchored day-by-day and re-derived
by counting, exactly as the Coucal Clock does: พ.ศ. ๒๕๖๙ from
Thai PBS, ปฏิทินวันพระ ๒๕๖๙,
พ.ศ. ๒๕๗๐ from
myhora,
ปฏิทินวันพระ ๒๕๗๐ cross-checked against
kapook on five festival dates.
The ๒๕๗๐ table is published ahead of the กรมการศาสนา confirmation expected around
September ๒๕๖๙, and will be reconfirmed then.
The Northern reading follows documented usage: Lan Na numbers its lunar months two ahead
of the central reckoning (จ.ศ. = ค.ศ. − 638, turning at Songkran; see
Chula Sakarat), the waning day is
แฮม, the sabbath is วันศีล, and the full-moon festival names (ยี่เป็ง, เดือนสิบเป็ง …) are derived
from the Northern month number. The year-animal forms ไจ้ and เป้า are attested directly on
digitised Lanna astrology manuscripts.