Synopsis There are many books dealing with this specialized subject, but when the Author engaged himself in this work he found from his study and experience that the Conservation Tables in circulation are not very comprehensive and suffered mainly from two shortcomings-inaccuracy and intricacy. This work tries to rectify both. On this topic Author's cyclopedic work of interchanging Gregorian and Hijrah dates from 120 BH to 2010 AH (506 AD to 2571 AD) has already published under the title of a compendium of Muslim and Christian Dates. But in the present title Author has specifically compiled the Julian Era dates from 564 AD to 1582 AD (60 BH to 990 AH) and the Gregorian Era dates from 1583 AD (991 AH) onwards. This work consists of four chapters in all. Chapter -I is exclusively devoted to the delineating the inadequacy of the extant conservation tables; adoption of the new style dates; interchanging of the old and new style dates and the Muslim day and the Christian day. Chapter -II is concerned with interchanging of the Hijrah and Christian dates from 564 AD (60BH) onwards. Chapter III deals with the formulas to calculate the Julian or the Gregorian date of the first day of any lunar month from 564 AD (60BH) onwards. Chapter IV is exclusively for interchanging of the old and new style dates. This handbook of interchanging Muslim and Christian Era dates has been prepared after considerable study and labour with the hope that it will be useful to students and scholars as well as laymen alike.