Bug in WinCmd 5.11 FTP time offset in SynchronizeDirs

[Garlin007]

I believe I have discovered a bug in version 5.11. I have also verified that this bug also exists in version 5.51.

If you use the FTP time offset, and set a negative offset like -7, and there is a file on the server before 6:59 on 2002/12/01 or 2003/03/01, then WinCmd calculates an incorrect date to match to the local file. Specifically, for the date 2002/12/01 06:00, instead of calculationg 2002/11/30 23:00 it calculates 2002/11/31 23:00. Likewise, for 2003/03/01 06:00 it calculates 2003/02/31 23:00. It appears that the algorithm for calculating the dates does not account for months that have fewer than 31 days. It is possible that this problem exists for other short months - but I have no files on the server with dates on the first days of May, July, or October to test this theory.