Manejo de DateTime en C#

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DateTime Subtraction Operator  [C#]See Also
DateTime Structure | DateTime Members | System Namespace | Managed Extensions for C++ Programming 
Language
C#

C++

JScript

Visual Basic

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Subtracts a specified DateTime or TimeSpan from a specified DateTime.

Overload List
Subtracts a specified date and time from another specified date and time, yielding a time interval.

Supported by the .NET Compact Framework.

[Visual Basic] Subtraction Operator (DateTime, DateTime)
[C#] public static TimeSpan operator -(DateTime, DateTime);
[C++] public: static TimeSpan op_Subtraction(DateTime, DateTime);
[JScript] Subtraction Operator (DateTime, DateTime)
Subtracts a specified time interval from a specified date and time, yielding a new date and time.

Supported by the .NET Compact Framework.

[Visual Basic] Subtraction Operator (DateTime, TimeSpan)
[C#] public static DateTime operator -(DateTime, TimeSpan);
[C++] public: static DateTime op_Subtraction(DateTime, TimeSpan);
[JScript] Subtraction Operator (DateTime, TimeSpan)
Example
[Visual Basic, C#, C++] The following sample demonstrates the Subtract method and operator.

[Visual Basic, C#, C++] Note   This example shows how to use one of the overloaded versions of the subtraction operator. For other examples that might be available, see the individual overload topics.
[Visual Basic] 
Dim date1 As New System.DateTime(1996, 6, 3, 22, 15, 0)
Dim date2 As New System.DateTime(1996, 12, 6, 13, 2, 0)
Dim date3 As New System.DateTime(1996, 10, 12, 8, 42, 0)

Dim diff1 As System.TimeSpan
' diff1 gets 185 days, 14 hours, and 47 minutes.
diff1 = date2.Subtract(date1)

Dim date4 As System.DateTime
' date4 gets 4/9/1996 5:55:00 PM.
date4 = date3.Subtract(diff1)

Dim diff2 As System.TimeSpan
' diff2 gets 55 days 4 hours and 20 minutes.
diff2 = System.DateTime.op_Subtraction(date2, date3)

Dim date5 As System.DateTime
' date5 gets 4/9/1996 5:55:00 PM.
date5 = System.DateTime.op_Subtraction(date1, diff2)

[C#] 
System.DateTime date1 = new System.DateTime(1996, 6, 3, 22, 15, 0);
System.DateTime date2 = new System.DateTime(1996, 12, 6, 13, 2, 0);
System.DateTime date3 = new System.DateTime(1996, 10, 12, 8, 42, 0);

// diff1 gets 185 days, 14 hours, and 47 minutes.
System.TimeSpan diff1 = date2.Subtract(date1);

// date4 gets 4/9/1996 5:55:00 PM.
System.DateTime date4 = date3.Subtract(diff1);

// diff2 gets 55 days 4 hours and 20 minutes.
System.TimeSpan diff2 = date2 - date3;

// date5 gets 4/9/1996 5:55:00 PM.
System.DateTime date5 = date1 - diff2;

Seguro que con eso ya podrías implementar algo