Most (all?) western countries use the year of the birth of the Lord Jesus Christ as the 0 year for their calenders, wht are some other calenders current being used in the world and what is their 0 year based on?
In the scientific community, especially the paleoanthropology/paleontology/geology/paleoclimate etc fields, they use a system of "years before present" or BP. They established the year 1950 as the "present" to which that refers, so technically 1950 AD would be their "year 0".
The Muslim calendar is a lunar-based calendar and year 1 is the year the Prophet moved from Mecca to Medina, the event known as the Hijrah (not to be confused with the Hijra in India). The Latin shorthand for the Islamic calendar is AH (Anno Hegira).
The date today is the 27th of March 2015; in the Islamic calendar, it's the 6th of Jamadil Akhir 1436
Thailand follows the Buddhist calendar - the year here is 2558, based on Buddha's birth date.