[[Microsoft]] uses the "'''Kuwaiti algorithm'''" to convert between dates in the Western standard [[Gregorian calendar]] and dates in the [[Islamic]] [[Islamic calendar|Hijri]] [[calendar]]. There is no fixed correspondence defined in advance between the Gregorian [[solar calendar]] and the Islamic [[lunar calendar]], since the latter is defined by the visibility of the new moon by religious authorities and can therefore vary by a day or two, depending on the particular Islamic authority, weather conditions, and other variables. As an attempt to make conversions between the calendars somewhat predictable, this [[algorithm]] is based on statistical analysis of historical data from [[Kuwait]]. The algorithm is inexact due to the use of statistical analysis, and conversions using this algorithm can often be in error by a day or two.
