如何获取日期时间月份开始和结束日期？

Question

How to get the start date and end date of month in different variable. I have tried this and I get the start date but unable to find the end date

DateTime startDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1).ToString("yyyy-MM-dd HH:mm:ss.fff");
DateTime  endDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1).AddDays(30).ToString("yyyy-MM-dd HH:mm:ss.fff");

This logic fails when month end date is 31 and 28 or 29. Your Help are surely appretiated.

Answer 1

您可以像这样计算endDate ：

DateTime endDate = startDate.AddMonths(1).AddDays(-1);

Answer 2

To get First Date

public DateTime FirstDayOfMonth(DateTime dateTime)
{
   return new DateTime(dateTime.Year, dateTime.Month, 1);
}

To get Last Date

public DateTime LastDayOfMonth(DateTime dateTime)
{
   DateTime firstDayOfTheMonth = new DateTime(dateTime.Year, dateTime.Month, 1);
   return firstDayOfTheMonth.AddMonths(1).AddDays(-1);
}

Answer 3

DateTime endDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1)
                       .AddMonths(1).AddDays(-1);

Answer 4

You already had the start date :

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

There's a method to get the number of days in a month (and Looking at the IL code, it seems that this way is more efficient than the other answers, though unless you're going to do it a billion time, I doubt there will be any difference) :

int daysInMonth = DateTime.DaysInMonth(DateTime.Now.Year, DateTime.Now.Month);
DateTime monthEndDate = new DateTime(DateTime.Now.Year, DateTime.Now.Month, daysInMonth);

Answer 5

For first date:

DateTime first_date = new DateTime(DateTimePicker.Value.Year, DateTimePicker.Value.Month, 1);

For last date:

DateTime last_date = new DateTime(DateTimePicker.Value.Year, DateTimePicker.Value.Month, DateTime.DaysInMonth(DateTimePicker.Value.Year, DateTimePicker.Value.Month));