有助于了解***将格里高利历称为Masihi。谷歌搜索hijrah to masihi converter将此页面作为第二个打击： http://www.islamicity.com/PrayerTimes/defaultHijriConv.asp

It helps to know that muslims refer to the Gregorian calendar as Masihi. Googling for "hijrah to masihi converter" turns up this page as the second hit: http://www.islamicity.com/PrayerTimes/defaultHijriConv.asp

javascript代码包含两个函数 GregToIsl 和 IslToGreg 可以满足您的需求。

The javascript is code contains two functions GregToIsl and IslToGreg that does what you want.

有版权声明那个页面所以你不应该简单地复制粘贴代码。但是这些函数足够短，你可以从中提取相关的数学。

There is a copyright notice on that page so you shouldn't simply copy-paste the code. But the functions are short enough for you to extract the relevant maths out of.

数学/算法本身已经有近千年的历史了，所以它不应该有任何合法的数学限制。

The maths/algorithm itself is almost a thousand years old so it shouldn't have any legal restriction.