CODEWITHSUNDEEP
c#
learning
learning

Reputation: 11725

set DateTime to start of month

How can I set a DateTime to the first of the month in C#?

Upvotes: 110

Views: 109586

Answers (9)

Søren
Søren

Reputation: 6787

I've just create some extension methods based on Nick answer and others on the SO

public static class DateTimeExtensions 
{
    /// <summary>
    /// get the datetime of the start of the week
    /// </summary>
    /// <param name="dt"></param>
    /// <param name="startOfWeek"></param>
    /// <returns></returns>
    /// <example>
    /// DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Monday);
    /// DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Sunday);
    /// </example>
    /// <remarks>http://stackoverflow.com/a/38064/428061</remarks>
    public static System.DateTime StartOfWeek(this System.DateTime dt, DayOfWeek startOfWeek)
    {
        var diff = dt.DayOfWeek - startOfWeek;
        if (diff < 0)
            diff += 7;

        return dt.AddDays(-1 * diff).Date;
    }

    /// <summary>
    /// get the datetime of the start of the month
    /// </summary>
    /// <param name="dt"></param>
    /// <returns></returns>
    /// <remarks>http://stackoverflow.com/a/5002582/428061</remarks>
    public static System.DateTime StartOfMonth(this System.DateTime dt) =>
        new System.DateTime(dt.Year, dt.Month, 1);


    /// <summary>
    /// get datetime of the start of the year
    /// </summary>
    /// <param name="dt"></param>
    /// <returns></returns>
    public static System.DateTime StartOfYear(this System.DateTime dt) => 
         new System.DateTime(dt.Year, 1, 1);

}

Upvotes: 2

Ann Sara
Ann Sara

Reputation: 69

Hope this helps you.

textbox1.Text = "01-" + DateTime.Now.ToString("MMM-yyyy");

Upvotes: 0

Jay Shah
Jay Shah

Reputation: 3771

var currentDate = DateTime.UtcNow.Date;
var startDateTimeOfCurrentMonth = currentDate.AddDays(-(currentDate.Day - 1));

Upvotes: -2

Nick Jones
Nick Jones

Reputation: 6493

var now = DateTime.Now;
var startOfMonth = new DateTime(now.Year,now.Month,1);

Upvotes: 220

fubo
fubo

Reputation: 45947

public static DateTime FirstDayOfMonth(this DateTime current)
{
    return current.AddDays(1 - current.Day);
}

Upvotes: 15

Colin Banbury
Colin Banbury

Reputation: 891

A bit late to the party but here's an extension method that did the trick for me

public static class DateTimeExtensions
{
  public static DateTime FirstDayOfMonth(this DateTime dt)
  {
    return new DateTime(dt.Year, dt.Month, 1);
  }
}

Upvotes: 9

nayato
nayato

Reputation: 83

This should be efficient and correct:

DateTime RoundDateTimeToMonth(DateTime time)
{
    long ticks = time.Ticks;
    return new DateTime((ticks / TimeSpan.TicksPerDay - time.Day + 1) * TimeSpan.TicksPerDay, time.Kind);
}

Here ticks / TimeSpan.TicksPerDay returns count of full days up to given time and - time.Day + 1 resets this count to the beginning of month.

Upvotes: 0

V4Vendetta
V4Vendetta

Reputation: 38210

Something like this would work

DateTime firstDay = DateTime.Today.AddDays(1 - DateTime.Today.Day);

Upvotes: 42

rotman
rotman

Reputation: 1651

DateTime now = DateTime.Now;
DateTime date = new DateTime(now.Year, now.Month, 1);

You can use anything else instead of DateTime.Now

Upvotes: 2

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