Point 1. B. E. and A. D.

The term khrdsa$gka$ra$ּd 'Christian era' (abbreviated khOּ sO4ּ ) is used when referring to the chronologic system reckoned from the date of the birth of Christ.

The term phu2dtha2sa$gka$ra$ּd or phra2phu2dtha2sa$gka$ra$ּd  'Buddhist era' (abbreviated phOּ sO4ּ) is used when referring to the chronologic system reckoned from the date of the death of the Buddha. Different Buddhist countries have slightly different dates for this event, but in Thailand it is reckoned to be 543 years before the beginning of the Christian era. Thus it is now A. D. 1947, but in Thailand it is B. E. 2490.

To determine the year according to the Buddhist era, add 543 to the year according to the Christian era. To determine the year according to the Christian era, subtract 543 from the year according to the Buddhist era.