You need to learn to research things on your own. in C#, date and time can be accessed extremely easily from within System.DateTime, and interfacing the serial port with C# .NET 2.0 is as trivial as dragging-and-dropping a System.IO.Ports.SerialPort control into your project, and playing with the methods and members. If you know C#, it should take you like 10 minutes, and in 2 minutes you could have searched and found out about both of those objects. If you don't know C#, go buy a book or search the web, and learn how to use it.
As for the microcontroller side, there are TONS of examples of serial port interfacing on the web, there is absolutely no reason that people should need to re-type that information here when you can easily find it yourself by just searching google.
If you try to do it and get stuck, then you can ask more specific questions, but obviously you have not done any work of your own, and haven't even taken the time to do your own research, so don't expect us to do it for you. It's not our job to sit around handing out pre-written code for every possible project people come along and ask about.