Common C # datetime date calculations

Today

DateTime.Now.Date.ToShortDateString ();

Yesterday, it was today's date minus one.

DateTime.Now.AddDays (-1). ToShortDateString ();

Tomorrow, in the same vein, add a

DateTime.Now.AddDays (1). ToShortDateString ();

This week, knowing that the day of the week is the first day of the week and that the first day of the week is a few days ago, it is important to note that every week here is from Sunday to Saturday

DateTime.Now.AddDays (Convert.todouble (0-convert.toint16 (DateTime.Now.DayOfWeek))). ToShortDateString ();

DateTime.Now.AddDays (Convert.todouble (6-convert.toint16 (DateTime.Now.DayOfWeek))). ToShortDateString ();

If you do not understand, then look at the Chinese display of the day of the week should understand the method

Since DayOfWeek returns the number of days of the week, we want to convert it into Chinese characters to facilitate our reading, some people may use switch to a control, in fact, not so troublesome

string[] Day = new string[] {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

Day[convert.toint16 (DateTime.Now.DayOfWeek)];

Last week, the same thing, a week is 7 days, last week is this week minus 7 days, and next week is the same

DateTime.Now.AddDays (Convert.todouble (0-convert.toint16 (DateTime.Now.DayOfWeek))-7). ToShortDateString ();

DateTime.Now.AddDays (Convert.todouble (6-convert.toint16 (DateTime.Now.DayOfWeek))-7). ToShortDateString ();

Next week

DateTime.Now.AddDays (Convert.todouble ((0-convert.toint16 (DateTime.Now.DayOfWeek)) + 7). ToShortDateString ();

DateTime.Now.AddDays (Convert.todouble ((6-convert.toint16 (DateTime.Now.DayOfWeek)) + 7). ToShortDateString ();

This month, many people will say that the first day of this month is definitely number 1th, and the last day is the next month minus another day. Of course it's right.

The general wording

DateTime.Now.Year.ToString () + DateTime.Now.Month.ToString () + "1"; First day

DateTime.Parse (DateTime.Now.Year.ToString () + DateTime.Now.Month.ToString () + "1"). AddMonths (1). AddDays (-1). ToShortDateString ();//Last Day

It's easier to use ToString's character formatting in C #

DateTime.Now.ToString ("yyyy-mm-01");

DateTime.Parse (DateTime.Now.ToString ("yyyy-mm-01")). AddMonths (1). AddDays (-1). ToShortDateString ();

Last month, minus one month

DateTime.Parse (DateTime.Now.ToString ("yyyy-mm-01")). AddMonths (-1). ToShortDateString ();

DateTime.Parse (DateTime.Now.ToString ("yyyy-mm-01")). AddDays (-1). ToShortDateString ();

Next month, add a month.

DateTime.Parse (DateTime.Now.ToString ("yyyy-mm-01")). AddMonths (1). ToShortDateString ();

DateTime.Parse (DateTime.Now.ToString ("yyyy-mm-01")). AddMonths (2). AddDays (-1). ToShortDateString ();

After 7 days

DateTime.Now.Date.ToShortDateString ();

DateTime.Now.AddDays (7). ToShortDateString ();

7 days ago

DateTime.Now.AddDays (-7). ToShortDateString ();

DateTime.Now.Date.ToShortDateString ();

This year, formatting with ToString's characters makes it easy to figure out the first and last day of the year

DateTime.Parse (DateTime.Now.ToString ("yyyy-01-01")). ToShortDateString ();

DateTime.Parse (DateTime.Now.ToString ("yyyy-01-01")). AddYears (1). AddDays (-1). ToShortDateString ();

Last year, no more explaining.

DateTime.Parse (DateTime.Now.ToString ("yyyy-01-01")). AddYears (-1). ToShortDateString ();

DateTime.Parse (DateTime.Now.ToString ("yyyy-01-01")). AddDays (-1). ToShortDateString ();

Next year

DateTime.Parse (DateTime.Now.ToString ("yyyy-01-01")). AddYears (1). ToShortDateString ();

DateTime.Parse (DateTime.Now.ToString ("yyyy-01-01")). AddYears (2). AddDays (-1). ToShortDateString ();

This quarter, many people will feel the difficulty here, need to write a long process to judge. In fact, we all know that four quarters a year, three months a quarter

First we push the date to the first month of the quarter, and then the first day of the month is the first day of the quarter.

DateTime.Now.AddMonths (0-((datetime.now.month-1)% 3)). ToString ("yyyy-mm-01");

Similarly, the last day of the quarter is the first day of the next quarter minus one

DateTime.Parse (DateTime.Now.AddMonths (3-((datetime.now.month-1)% 3)). ToString ("yyyy-mm-01")). AddDays (-1). ToShortDateString ();

Next quarter, I believe you all know .... Call it

DateTime.Now.AddMonths (3-((datetime.now.month-1)% 3)). ToString ("yyyy-mm-01");

DateTime.Parse (DateTime.Now.AddMonths (6-((datetime.now.month-1)% 3)). ToString ("yyyy-mm-01")). AddDays (-1). ToShortDateString ();

Last quarter

DateTime.Now.AddMonths ( -3-((datetime.now.month-1)% 3)). ToString ("yyyy-mm-01");

DateTime.Parse (DateTime.Now.AddMonths (0-((datetime.now.month-1)% 3)). ToString ("yyyy-mm-01")). AddDays (-1). ToShortDateString ();

Common C # datetime date calculations