Method dateCorrection is not working

[alhoqbani]

The method dateCorrection is supposed to calculate the correction factor for the Hijri date conversion based on Um Alqura calendar. It supports date range 1420-1459, and should return a correction factor range from -2 to +2.

However, the method is not working and almost always returns 0.

I have tested every month from the supported range (1420-1459). Out of 456 tested months, only 21 months returned a value different than 0, which does not seem right.

This commit a121197 adds a test to check the functionality of the method.