DateTime and CTime cooperation

Sometimes you might want to pass a current time from managed application to unmanaged and vice versa. The one way to pass time from C# to, lets say, MFC is to calculate total number of seconds from 1.1.70 until current time. Then you will marshal this long value to MFC (probably using COM or network, depends on what you doing) and will create CTime class from it. Here is something you have to consider: DateTime structure by default represents local time, while CTime represents GMT time. Lets say I live in Israel (GMT +2) and my current time is 9:00 AM. Next step I calculating long of total seconds and send it to MFC’s CTime. Now, the CTime thinks it is GMT time. Therefore when I presenting CTIme using ‘Format’ method, I receiving… 11:00 AM. You see, ‘Format’ method counts on fact that CTime is GMT time, and during convertion to string adds GMT delta (in my case + 2 hours). So if you will pass to CTime local time, ‘Format’ method will convert local time to local time again.  The point of this story, is you will always have to pass to CTime class GMT time. if not, ‘Format’ method will represent incorrect values (unless you work in +0 time zone). By the way: in case you want to represent original CTime time, instead of ‘Format’ method use ‘FormatGmt’.