DateTime.Subtract Method (DateTime)
Subtracts the specified date and time from this instance.
Assembly: mscorlib (in mscorlib.dll)
Parameters
 value

Type:
System.DateTime
The date and time value to subtract.
Return Value
Type: System.TimeSpanA time interval that is equal to the date and time represented by this instance minus the date and time represented by value.
Exception  Condition 

ArgumentOutOfRangeException 
The Subtract(DateTime) method determines the difference between two dates. To subtract a time interval from the current instance, call the Subtract(TimeSpan) method. To subtract a particular time interval from the current instance, call the method that adds that time interval to the current date, and supply a negative value as the method argument. For example, to subtract two months from the current date, call the AddMonths(Int32) method with a value of 2.
If the date and time of the current instance is earlier than value, the method returns a TimeSpan object that represents a negative time span. That is, the value of all of its nonzero properties (such as Days or Ticks) is negative.
TheSubtract(DateTime) method does not consider the value of the Kind property of the two DateTime values when performing the subtraction. Before subtracting DateTime objects, ensure that the objects represent times in the same time zone. Otherwise, the result will include the difference between time zones.
Note 

The DateTimeOffset.Subtract(DateTimeOffset) method does consider the difference between time zones when performing the subtraction. 
The following example demonstrates the Subtract method and the subtraction operator.
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)
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1