How do I get the last day of a month?
How can I find the last day of the month in C#?
For example, if I have the date 03/开发者_如何转开发08/1980, how do I get the last day of month 8 (in this case 31)?
The last day of the month you get like this, which returns 31:
DateTime.DaysInMonth(1980, 08);
var lastDayOfMonth = DateTime.DaysInMonth(date.Year, date.Month);
If you want the date, given a month and a year, this seems about right:
public static DateTime GetLastDayOfMonth(this DateTime dateTime)
{
return new DateTime(dateTime.Year, dateTime.Month, DateTime.DaysInMonth(dateTime.Year, dateTime.Month));
}
Substract a day from the first of next month:
DateTime lastDay = new DateTime(MyDate.Year,MyDate.Month+1,1).AddDays(-1);
Also, in case you need it to work for December too:
DateTime lastDay = new DateTime(MyDate.Year,MyDate.Month,1).AddMonths(1).AddDays(-1);
You can find the last date of any month by this code:
var now = DateTime.Now;
var startOfMonth = new DateTime(now.Year, now.Month, 1);
var DaysInMonth = DateTime.DaysInMonth(now.Year, now.Month);
var lastDay = new DateTime(now.Year, now.Month, DaysInMonth);
// Use any date you want, for the purpose of this example we use 1980-08-03.
var myDate = new DateTime(1980,8,3);
var lastDayOfMonth = new DateTime(myDate.Year, myDate.Month, DateTime.DaysInMonth(myDate.Year, myDate.Month));
You can find the last day of the month by a single line of code:
int maxdt = (new DateTime(dtfrom.Year, dtfrom.Month, 1).AddMonths(1).AddDays(-1)).Day;
From DateTimePicker:
First date:
DateTime first_date = new DateTime(DateTimePicker.Value.Year, DateTimePicker.Value.Month, 1);
Last date:
DateTime last_date = new DateTime(DateTimePicker.Value.Year, DateTimePicker.Value.Month, DateTime.DaysInMonth(DateTimePicker.Value.Year, DateTimePicker.Value.Month));
You can extend DateTime as follows;
public static class DateTimeMethods
{
public static DateTime StartOfMonth(this DateTime date)
{
return new DateTime(date.Year, date.Month, 1, 0, 0, 0);
}
public static DateTime EndOfMonth(this DateTime date)
{
return date.StartOfMonth().AddMonths(1).AddSeconds(-1);
}
}
and use it as follows;
DateTime today = DateTime.Now;
DateTime startOfMonth = today.StartOfMonth();
DateTime endOfMonth = today.EndOfMonth();
This will display the last date of the next month. You can add the month of the year you want to return by adding or substracting it from AddMonths(x)
DateTime.Now.AddMonths(2).AddDays(-DateTime.Now.Day)
To get last day of a month in a specific calendar - and in an extension method -:
public static int DaysInMonthBy(this DateTime src, Calendar calendar)
{
var year = calendar.GetYear(src); // year of src in your calendar
var month = calendar.GetMonth(src); // month of src in your calendar
var lastDay = calendar.GetDaysInMonth(year, month); // days in month means last day of that month in your calendar
return lastDay;
}
example on 05/07/2021
DateTime.Now.Day;
Result: 5
DateTime.Now.AddMonths(+1).AddDays(-DateTime.Now.Day).ToString("yyyy-MM-dd");
result: 2021/07/31
Another way to get end date:
private static DateTime GetMonthEndDate(DateTime date)
{
DateTime endDate = date;
int endDateMonth = endDate.Month;
while (endDateMonth == endDate.Month)
endDate = endDate.AddDays(1);
endDate = endDate.AddDays(-1);
return endDate;
}
I only wanted to fire code on the last day of every month, it's a simple as this...
if (DateTime.UtcNow.AddDays(1).Day != 1)
{
// Tomorrow is not the first...
return;
}
I don't know C# but, if it turns out there's not a convenient API way to get it, one of the ways you can do so is by following the logic:
today -> +1 month -> set day of month to 1 -> -1 day
Of course, that assumes you have date math of that type.
This formula reflects @RHSeeger's thought as a simple solution to get (in this example) the last day of the 3rd month (month of date in cell A1 + 4 with the first day of that month minus 1 day):
=DATE(YEAR(A1);MONTH(A1)+4;1)-1
Very precise, inclusive February's in leap years :)
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