Add 2400001 to the Modified Julian date. This number is the Julian date. For example, if the Modified Julian date is 44238 then the Julian date is 44238 + 2400001 = 2444239.
Find the month/day/year equivalent of the Julian date by using an online calculator such as the one developed by Numerical Recipes. If we put in the Julian date 2444239 from the last step, it shows that is equivalent to January 1, 1980.
Find the month/day/year equivalent of the modified Julian date using tables if you do not have access to an online calculator. If you look up January 1, 1980 in these tables, the Modified Julian date will be 44238. NASA makes tables of dates during the last three decades available online. You can also find these tables in a reference work at your local library.