DateTimeOffset.AddDays(Double) Method

Reference

Definition

Namespace:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: DateTimeOffset.cs

Source:: DateTimeOffset.cs

Source:: DateTimeOffset.cs

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Returns a new DateTimeOffset object that adds a specified number of whole and fractional days to the value of this instance.

public:
 DateTimeOffset AddDays(double days);

public DateTimeOffset AddDays (double days);

member this.AddDays : double -> DateTimeOffset

Public Function AddDays (days As Double) As DateTimeOffset

Parameters

days: Double

A number of whole and fractional days. The number can be negative or positive.

Returns

DateTimeOffset

An object whose value is the sum of the date and time represented by the current DateTimeOffset object and the number of days represented by days.

Exceptions

ArgumentOutOfRangeException

The resulting DateTimeOffset value is less than DateTimeOffset.MinValue.

-or-

The resulting DateTimeOffset value is greater than DateTimeOffset.MaxValue.

Examples

The following example uses the AddDays method to list the dates that fall on Monday, the start of the work week, in March 2008.

DateTimeOffset workDay = new DateTimeOffset(2008, 3, 1, 9, 0, 0,
                   DateTimeOffset.Now.Offset);
int month = workDay.Month;
// Start with the first Monday of the month
if (workDay.DayOfWeek != DayOfWeek.Monday)
{
   if (workDay.DayOfWeek == DayOfWeek.Sunday)
      workDay = workDay.AddDays(1);
   else
      workDay = workDay.AddDays(8 - (int)workDay.DayOfWeek);
}
Console.WriteLine("Beginning of Work Week In {0:MMMM} {0:yyyy}:", workDay);
// Add one week to the current date
do
{
   Console.WriteLine("   {0:dddd}, {0:MMMM}{0: d}", workDay);
   workDay = workDay.AddDays(7);
} while (workDay.Month == month);
// The example produces the following output:
//    Beginning of Work Week In March 2008:
//       Monday, March 3
//       Monday, March 10
//       Monday, March 17
//       Monday, March 24
//       Monday, March 31

let workDay = DateTimeOffset(2008, 3, 1, 9, 0, 0, DateTimeOffset.Now.Offset)
let month = workDay.Month

// Start with the first Monday of the month
let mutable workDay = 
    match workDay.DayOfWeek with
    | DayOfWeek.Monday ->
        workDay
    | DayOfWeek.Sunday ->
        workDay.AddDays 1
    | _ ->
        workDay.AddDays(8. - float workDay.DayOfWeek)

printfn $"Beginning of Work Week In {workDay:MMMM} {workDay:yyyy}:"

// Add one week to the current date
while workDay.Month = month do
    printfn $"   {workDay:dddd}, {workDay:MMMM}{workDay: d}"
    workDay <- workDay.AddDays 7

// The example produces the following output:
//    Beginning of Work Week In March 2008:
//       Monday, March 3
//       Monday, March 10
//       Monday, March 17
//       Monday, March 24
//       Monday, March 31

Dim workDay As New DateTimeOffset(#3/1/2008 9:00AM#, _
                   DateTimeOffset.Now.Offset)
Dim month As Integer = workDay.Month
' Start with the first Monday of the month
If workDay.DayOfWeek <> DayOfWeek.Monday Then
   If workDay.DayOfWeek = DayOfWeek.Sunday Then
      workDay = workDay.AddDays(1)
   Else   
      workDay = workDay.AddDays(8 - CInt(workDay.DayOfWeek))
   End If
End If
Console.WriteLine("Beginning of Work Week In {0:MMMM} {0:yyyy}:", workDay)
' Add one week to the current date 
Do While workDay.Month = month
   Console.WriteLine("   {0:dddd}, {0:MMMM}{0: d}", workDay)
   workDay = workDay.AddDays(7)
Loop        
' The example produces the following output:
'    Beginning of Work Week In March 2008:
'       Monday, March 3
'       Monday, March 10
'       Monday, March 17
'       Monday, March 24
'       Monday, March 31

Remarks

The fractional part of the days parameter is the fractional part of a day. For example, 4.5 is equivalent to 4 days, 12 hours, 0 minutes, 0 seconds, 0 milliseconds.

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

Note

This method returns a new DateTimeOffset object. It does not modify the value of the current object by adding days to its date and time.

Because a DateTimeOffset object does not represent the date and time in a specific time zone, the AddDays method does not consider a particular time zone's adjustment rules when it performs date and time arithmetic.

Converting time intervals of less than a day to a fraction can involve a loss of precision. If this is problematic, you can use the Add method, which enables you to specify more than one kind of time interval in a single method call and eliminates the need to convert time intervals to fractional parts of a day.

Applies to

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