Get the previous month's first and last day dates in c#

Question

I can\'t think of an easy one or two liner that would get the previous months first day and last day.

I am LINQ-ifying a survey web app, and they squeezed a new requ

Answer 1

This is a take on Mike W's answer:

internal static DateTime GetPreviousMonth(bool returnLastDayOfMonth)
{
    DateTime firstDayOfThisMonth = DateTime.Today.AddDays( - ( DateTime.Today.Day - 1 ) );
    DateTime lastDayOfLastMonth = firstDayOfThisMonth.AddDays (-1);
    if (returnLastDayOfMonth) return lastDayOfLastMonth;
    return firstDayOfThisMonth.AddMonths(-1);
}

You can call it like so:

dateTimePickerFrom.Value = GetPreviousMonth(false);
dateTimePickerTo.Value = GetPreviousMonth(true);

Answer 2

DateTime now = DateTime.Now;
int prevMonth = now.AddMonths(-1).Month;
int year = now.AddMonths(-1).Year;
int daysInPrevMonth = DateTime.DaysInMonth(year, prevMonth);
DateTime firstDayPrevMonth = new DateTime(year, prevMonth, 1);
DateTime lastDayPrevMonth = new DateTime(year, prevMonth, daysInPrevMonth);
Console.WriteLine("{0} {1}", firstDayPrevMonth.ToShortDateString(),
  lastDayPrevMonth.ToShortDateString());

Answer 3

DateTime LastMonthLastDate = DateTime.Today.AddDays(0 - DateTime.Today.Day);
DateTime LastMonthFirstDate = LastMonthLastDate.AddDays(1 - LastMonthLastDate.Day);

Answer 4

The way I've done this in the past is first get the first day of this month

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

Then subtract a day to get end of last month

dLastDayOfLastMonth = dFirstDayOfThisMonth.AddDays (-1);

Then subtract a month to get first day of previous month

dFirstDayOfLastMonth = dFirstDayOfThisMonth.AddMonths(-1);

Answer 5

An approach using extension methods:

class Program
{
    static void Main(string[] args)
    {
        DateTime t = DateTime.Now;

        DateTime p = t.PreviousMonthFirstDay();
        Console.WriteLine( p.ToShortDateString() );

        p = t.PreviousMonthLastDay();
        Console.WriteLine( p.ToShortDateString() );


        Console.ReadKey();
    }
}


public static class Helpers
{
    public static DateTime PreviousMonthFirstDay( this DateTime currentDate )
    {
        DateTime d = currentDate.PreviousMonthLastDay();

        return new DateTime( d.Year, d.Month, 1 );
    }

    public static DateTime PreviousMonthLastDay( this DateTime currentDate )
    {
        return new DateTime( currentDate.Year, currentDate.Month, 1 ).AddDays( -1 );
    }
}

See this link http://www.codeplex.com/fluentdatetime for some inspired DateTime extensions.

Answer 6

The canonical use case in e-commerce is credit card expiration dates, MM/yy. Subtract one second instead of one day. Otherwise the card will appear expired for the entire last day of the expiration month.

DateTime expiration = DateTime.Parse("07/2013");
DateTime endOfTheMonthExpiration = new DateTime(
  expiration.Year, expiration.Month, 1).AddMonths(1).AddSeconds(-1);