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DateTime.AddMilliseconds(Double) Method

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Definition

Namespace:
System
Assembly:
System.Runtime.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll
Source:
DateTime.cs
Source:
DateTime.cs
Source:
DateTime.cs

Returns a new DateTime that adds the specified number of milliseconds to the value of this instance.

public:
 DateTime AddMilliseconds(double value);
public DateTime AddMilliseconds (double value);
member this.AddMilliseconds : double -> DateTime
Public Function AddMilliseconds (value As Double) As DateTime

Parameters

value
Double

A number of whole and fractional milliseconds. The value parameter can be negative or positive. Note that this value is rounded to the nearest integer.

Returns

DateTime

An object whose value is the sum of the date and time represented by this instance and the number of milliseconds represented by value.

Exceptions

ArgumentOutOfRangeException

The resulting DateTime is less than DateTime.MinValue or greater than DateTime.MaxValue.

Examples

The following example uses the AddMilliseconds method to add one millisecond and 1.5 milliseconds to a DateTime value. It then displays each new value and displays the difference between it and the original value. The difference is displayed both as a time span and as a number of ticks. The example makes it clear that one millisecond equals 10,000 ticks. It also shows that fractional milliseconds are rounded before performing the addition; the DateTime value that results from adding 1.5 milliseconds to the original date is 2 milliseconds greater than the original date.

string dateFormat = "MM/dd/yyyy hh:mm:ss.fffffff";
DateTime date1 = new DateTime(2010, 9, 8, 16, 0, 0);
Console.WriteLine("Original date: {0} ({1:N0} ticks)\n",
                  date1.ToString(dateFormat), date1.Ticks);

DateTime date2 = date1.AddMilliseconds(1);
Console.WriteLine("Second date:   {0} ({1:N0} ticks)",
                  date2.ToString(dateFormat), date2.Ticks);
Console.WriteLine("Difference between dates: {0} ({1:N0} ticks)\n",
                  date2 - date1, date2.Ticks - date1.Ticks);

DateTime date3 = date1.AddMilliseconds(1.5);
Console.WriteLine("Third date:    {0} ({1:N0} ticks)",
                  date3.ToString(dateFormat), date3.Ticks);
Console.WriteLine("Difference between dates: {0} ({1:N0} ticks)",
                  date3 - date1, date3.Ticks - date1.Ticks);
// The example displays the following output:
//    Original date: 09/08/2010 04:00:00.0000000 (634,195,584,000,000,000 ticks)
//
//    Second date:   09/08/2010 04:00:00.0010000 (634,195,584,000,010,000 ticks)
//    Difference between dates: 00:00:00.0010000 (10,000 ticks)
//
//    Third date:    09/08/2010 04:00:00.0020000 (634,195,584,000,020,000 ticks)
//    Difference between dates: 00:00:00.0020000 (20,000 ticks)

let dateFormat = "MM/dd/yyyy hh:mm:ss.fffffff"
let date1 = DateTime(2010, 9, 8, 16, 0, 0)
printfn $"Original date: {date1.ToString dateFormat} ({date1.Ticks:N0} ticks)\n"

let date2 = date1.AddMilliseconds 1
printfn $"Second date:   {date2.ToString dateFormat} ({date2.Ticks:N0} ticks)"
printfn $"Difference between dates: {date2 - date1} ({date2.Ticks - date1.Ticks:N0} ticks)\n"

let date3 = date1.AddMilliseconds 1.5
printfn $"Third date:    {date3.ToString dateFormat} ({date3.Ticks:N0} ticks)"
printfn $"Difference between dates: {date3 - date1} ({date3.Ticks - date1.Ticks:N0} ticks)"

// The example displays the following output:
//    Original date: 09/08/2010 04:00:00.0000000 (634,195,584,000,000,000 ticks)
//
//    Second date:   09/08/2010 04:00:00.0010000 (634,195,584,000,010,000 ticks)
//    Difference between dates: 00:00:00.0010000 (10,000 ticks)
//
//    Third date:    09/08/2010 04:00:00.0020000 (634,195,584,000,020,000 ticks)
//    Difference between dates: 00:00:00.0020000 (20,000 ticks)

Dim dateFormat As String = "MM/dd/yyyy hh:mm:ss.fffffff" 
Dim date1 As Date = #09/08/2010 16:00#
Console.WriteLine("Original date: {0} ({1:N0} ticks)", _
                  date1.ToString(dateFormat), date1.Ticks)
Console.WriteLine()

Dim date2 As Date = date1.AddMilliseconds(1)
Console.WriteLine("Second date:   {0} ({1:N0} ticks)", _
                  date2.ToString(dateFormat), date2.Ticks)
Console.WriteLine("Difference between dates: {0} ({1:N0} ticks)", _
                  date2 - date1, date2.Ticks - date1.Ticks)                        
Console.WriteLine()

Dim date3 As Date = date1.AddMilliseconds(1.5)
Console.WriteLine("Third date:    {0} ({1:N0} ticks)", _
                  date3.ToString(dateFormat), date3.Ticks)
Console.WriteLine("Difference between dates: {0} ({1:N0} ticks)", _
                  date3 - date1, date3.Ticks - date1.Ticks)                        
' The example displays the following output:
'    Original date: 09/08/2010 04:00:00.0000000 (634,195,584,000,000,000 ticks)
'    
'    Second date:   09/08/2010 04:00:00.0010000 (634,195,584,000,010,000 ticks)
'    Difference between dates: 00:00:00.0010000 (10,000 ticks)
'    
'    Third date:    09/08/2010 04:00:00.0020000 (634,195,584,000,020,000 ticks)
'    Difference between dates: 00:00:00.0020000 (20,000 ticks)

Remarks

This method does not change the value of this DateTime. Instead, it returns a new DateTime whose value is the result of this operation.

The fractional part of value is the fractional part of a millisecond. For example, 4.5 is equivalent to 4 milliseconds and 5000 ticks, where one millisecond = 10000 ticks.

In .NET 6 and earlier versions, the value parameter is rounded to the nearest millisecond. In .NET 7 and later versions, the full Double precision of the value parameter is used. However, due to the inherent imprecision of floating point math, the resulting precision will vary.

Applies to

See also