We are living in 21st century, my question is, is Islamic calendar came after the invention of English calendar? As Islamic year going on is 1436(I don’t know exactly) and English year going on is 2015?? Please help, I'm debating on this with many people. Thanks in Advance
Did the Islamic calendar come after the invention of the English calendar? Yes and no.
The Hijri calendar (i.e. the Islamic calendar) counts years based on the Hijrah — the year Mohammad and his followers left Mecca for Madinah — which is actually about the halfway point in Muhammad's twenty-odd year long ministry, so it's correlation to "how old Islam is" is rather loose (which is only fair; did "Islam" start when Muhammad first received revelation? When he first started preaching? When the revelation was actually completed? When he died? And that's not even getting into the fact that most Muslims would claim Islam started way back when Adam first received revelation from the Almighty). It was implemented in the early seventh century, shortly after the prophet died.
The Gregorian calendar (i.e. the English calendar), on the other hand, actually wasn't invented until the 16th century, almost a thousand years later, but it was directly derived from the far older Julian calendar which was almost seven hundred years earlier than the Hijri.
Of course, the lunar calendar which the Hijri calendar itself is derived from has likely been in use since antiquity.
Also of note, unlike the Gregorian calendar, the Hijri calendar is purely a lunar calendar; while both the Hijri and the Gregorian "year" contain twelve months, the Hijri month is based entirely on lunar cycles (compared to the Gregorian month, which is a mostly-fixed number of days calculated so the "year" matches the solar cycle). As such, claiming that Islam (which is to say, the Hijri calendar) is 1436 years old only makes sense if you're using lunar years, as this would actually be equivalent to 1393 solar years.
In short, both calendars are actually older than each other, and 1436 = 1393. Comparing calendars like you're doing makes things crazy confusing: Regardless of which side you're on, this isn't likely a debate anyone's going to win any time soon without a few headaches.
The Islamic calendar counts years from the hijra of the Prophet in the year 622 of the Common Era. However, the counting of years according to the hijra era was actually introduced by the second caliph, Umar, according to some in the year 17 of the hijra, according to others one year earlier or later.
There is actually no such thing as the “English calendar”. The “Common” or “Christian” era has as its epoch the year 1, which Christian scholars used to think (probably wrongly) was the year in which Jesus was born. This system of dating is attested since the 5th century CE, and is first used systematically by the Venerable Bede in the early 8th century CE. In this sense it can probably be argued that the Islamic era is older than the Common/Christian era.
The standard reference work: http://referenceworks.brillonline.com/entries/encyclopaedia-of-islam-2/tarikh-COM_1184