Islamic vs Gregorian year

For a very rough conversion, multiply the Islamic year number by 0.97, and then add 622 to get the Gregorian year number. An Islamic year will be entirely within a Gregorian year of the same number in the year 20874. The Islamic calendar year of 1429 occurred entirely within the Gregorian calendar year of 2008. Such years occur once every 33 or 34 Islamic years (32 or 33 Gregorian years). More are listed here:
Islamic year within Gregorian year
Islamic Gregorian Difference
1060 1650 590
1093 1682 589
1127 1715 588
1161 1748 587
1194 1780 586
1228 1813 585
1261 1845 584
1295 1878 583
1329 1911 582
1362 1943 581
1396 1976 580
1429 2008 579
1463 2041 578
1496 2073 577
1530 2106 576
1564 2139 575
Because a hijri or Islamic lunar year is between 10 and 12 days shorter than a Gregorian year, it begins 10–12 days earlier in the Gregorian year following the Gregorian year in which the previous hijri year began. Once every 33.58 hijri years, or once every 32.58 Gregorian years, the beginning of a hijri year (1 Muharram) coincides with one of the first ten days of January. Subsequent hijri New Years move backward through the Gregorian year back to the beginning of January again, passing through each Gregorian month from December to January. To find the Gregorian year and approximate Gregorian month within which a specific hijri year begins, locate that hijri year within the table above. Subtract from it the hijri year after the previous hijri year which occurred within a single Gregorian year (the coinciding year). For the hijri year 1344, the previous coinciding hijri year was 1329, so subtract 1330 from 1344, yielding 14. Add 14 to the coinciding Gregorian year of 1911 yielding 1925. To determine the approximate Gregorian month within which the stated hijri year begins, divide 14 by 33 (the coincidence period) and multiply by 12 months yielding 5.5 months before January. Thus hijri year 1330 begins within July 1925.