如何在 C# 中仅知道当前时间找到一周的开始时间（周日和周一）？
就像是：
DateTime.Now.StartWeek(Monday);
GateKiller
问问题
329866 次
34 回答
863
使用扩展方法。他们是一切的答案，你知道的！;)
public static class DateTimeExtensions
{
public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;
return dt.AddDays(-1 * diff).Date;
}
}
可以按如下方式使用：
DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Monday);
DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Sunday);
于 2008-09-01T15:45:54.697 回答
102
我能想到的最快方法是：
var sunday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek);
如果您希望一周中的任何其他日子成为您的开始日期，您只需将 DayOfWeek 值添加到末尾
var monday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Monday);
var tuesday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Tuesday);
于 2013-01-30T16:45:11.170 回答
75
更冗长和文化意识：
System.Globalization.CultureInfo ci =
System.Threading.Thread.CurrentThread.CurrentCulture;
DayOfWeek fdow = ci.DateTimeFormat.FirstDayOfWeek;
DayOfWeek today = DateTime.Now.DayOfWeek;
DateTime sow = DateTime.Now.AddDays(-(today - fdow)).Date;
于 2008-09-01T15:47:47.953 回答
40
使用流畅的日期时间：
var monday = DateTime.Now.Previous(DayOfWeek.Monday);
var sunday = DateTime.Now.Previous(DayOfWeek.Sunday);
于 2009-09-04T12:26:34.640 回答
34
丑陋，但它至少给出了正确的日期
由系统设置周开始：
public static DateTime FirstDateInWeek(this DateTime dt)
{
while (dt.DayOfWeek != System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek)
dt = dt.AddDays(-1);
return dt;
}
没有：
public static DateTime FirstDateInWeek(this DateTime dt, DayOfWeek weekStartDay)
{
while (dt.DayOfWeek != weekStartDay)
dt = dt.AddDays(-1);
return dt;
}
于 2012-05-11T14:21:19.263 回答
12
让我们结合文化安全答案和扩展方法答案：
public static class DateTimeExtensions
{
public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
System.Globalization.CultureInfo ci = System.Threading.Thread.CurrentThread.CurrentCulture;
DayOfWeek fdow = ci.DateTimeFormat.FirstDayOfWeek;
return DateTime.Today.AddDays(-(DateTime.Today.DayOfWeek- fdow));
}
}
于 2008-09-01T20:43:35.557 回答
11
这会给你前一个星期天（我想）：
DateTime t = DateTime.Now;
t -= new TimeSpan ((int) t.DayOfWeek, 0, 0, 0);
于 2008-09-01T15:17:29.303 回答
11
星期一
DateTime startAtMonday = DateTime.Now.AddDays(DayOfWeek.Monday - DateTime.Now.DayOfWeek);
周日
DateTime startAtSunday = DateTime.Now.AddDays(DayOfWeek.Sunday- DateTime.Now.DayOfWeek);
于 2018-10-09T11:47:30.177 回答
10
这可能有点 hack，但是您可以将 .DayOfWeek 属性转换为 int（它是一个枚举，并且由于其基础数据类型没有更改，因此默认为 int）并使用它来确定一周的前一个开始.
DayOfWeek 枚举中指定的星期似乎从星期日开始，因此如果我们从该值中减去 1，则等于星期一在当前日期之前的天数。我们还需要将星期日 (0) 映射为等于 7，因此给定 1 - 7 = -6，星期日将映射到前一个星期一：-
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
dayOfWeek = dayOfWeek == 0 ? 7 : dayOfWeek;
DateTime startOfWeek = now.AddDays(1 - (int)now.DayOfWeek);
上周日的代码更简单，因为我们不必进行此调整：-
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
DateTime startOfWeek = now.AddDays(-(int)now.DayOfWeek);
于 2008-09-01T15:42:09.150 回答
6
using System;
using System.Globalization;
namespace MySpace
{
public static class DateTimeExtention
{
// ToDo: Need to provide culturaly neutral versions.
public static DateTime GetStartOfWeek(this DateTime dt)
{
DateTime ndt = dt.Subtract(TimeSpan.FromDays((int)dt.DayOfWeek));
return new DateTime(ndt.Year, ndt.Month, ndt.Day, 0, 0, 0, 0);
}
public static DateTime GetEndOfWeek(this DateTime dt)
{
DateTime ndt = dt.GetStartOfWeek().AddDays(6);
return new DateTime(ndt.Year, ndt.Month, ndt.Day, 23, 59, 59, 999);
}
public static DateTime GetStartOfWeek(this DateTime dt, int year, int week)
{
DateTime dayInWeek = new DateTime(year, 1, 1).AddDays((week - 1) * 7);
return dayInWeek.GetStartOfWeek();
}
public static DateTime GetEndOfWeek(this DateTime dt, int year, int week)
{
DateTime dayInWeek = new DateTime(year, 1, 1).AddDays((week - 1) * 7);
return dayInWeek.GetEndOfWeek();
}
}
}
于 2015-12-05T17:52:54.693 回答
4
将它们放在一起，与全球化并允许指定一周的第一天作为我们通话的一部分
public static DateTime StartOfWeek ( this DateTime dt, DayOfWeek? firstDayOfWeek )
{
DayOfWeek fdow;
if ( firstDayOfWeek.HasValue )
{
fdow = firstDayOfWeek.Value;
}
else
{
System.Globalization.CultureInfo ci = System.Threading.Thread.CurrentThread.CurrentCulture;
fdow = ci.DateTimeFormat.FirstDayOfWeek;
}
int diff = dt.DayOfWeek - fdow;
if ( diff < 0 )
{
diff += 7;
}
return dt.AddDays( -1 * diff ).Date;
}
于 2012-07-08T00:47:28.010 回答
4
var now = System.DateTime.Now;
var result = now.AddDays(-((now.DayOfWeek - System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek + 7) % 7)).Date;
于 2013-09-16T06:24:53.353 回答
3
第一步：创建一个静态类
public static class TIMEE
{
public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;
return dt.AddDays(-1 * diff).Date;
}
public static DateTime EndOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
int diff = (7 - (dt.DayOfWeek - startOfWeek)) % 7;
return dt.AddDays(1 * diff).Date;
}
}
第 2 步：使用此类获取一周的开始和结束日期
DateTime dt =TIMEE.StartOfWeek(DateTime.Now ,DayOfWeek.Monday);
DateTime dt1 = TIMEE.EndOfWeek(DateTime.Now, DayOfWeek.Sunday);
于 2019-04-04T11:34:50.450 回答
2
这会给你一周的第一个星期日的午夜：
DateTime t = DateTime.Now;
t -= new TimeSpan ((int) t.DayOfWeek, t.Hour, t.Minute, t.Second);
这会给你第一个星期一的午夜：
DateTime t = DateTime.Now;
t -= new TimeSpan ((int) t.DayOfWeek - 1, t.Hour, t.Minute, t.Second);
于 2008-09-01T15:53:42.697 回答
2
在 c# 中尝试使用此代码。使用此代码，您可以获得给定周的第一个日期和最后一个日期。这里星期日是第一天，星期六是最后一天，但您可以根据您的文化设置这两个日期
DateTime firstDate = GetFirstDateOfWeek(DateTime.Parse("05/09/2012").Date,DayOfWeek.Sunday);
DateTime lastDate = GetLastDateOfWeek(DateTime.Parse("05/09/2012").Date, DayOfWeek.Saturday);
public static DateTime GetFirstDateOfWeek(DateTime dayInWeek, DayOfWeek firstDay)
{
DateTime firstDayInWeek = dayInWeek.Date;
while (firstDayInWeek.DayOfWeek != firstDay)
firstDayInWeek = firstDayInWeek.AddDays(-1);
return firstDayInWeek;
}
public static DateTime GetLastDateOfWeek(DateTime dayInWeek, DayOfWeek firstDay)
{
DateTime lastDayInWeek = dayInWeek.Date;
while (lastDayInWeek.DayOfWeek != firstDay)
lastDayInWeek = lastDayInWeek.AddDays(1);
return lastDayInWeek;
}
于 2012-05-21T13:09:52.520 回答
2
尝试了几次，但没有解决从星期一开始的一周的问题，导致在星期日给我下一个星期一。因此，我对其进行了一些修改，并使其与以下代码一起使用：
int delta = DayOfWeek.Monday - DateTime.Now.DayOfWeek;
DateTime monday = DateTime.Now.AddDays(delta == 1 ? -6 : delta);
return monday;
于 2016-06-18T22:37:27.977 回答
1
以下方法应返回所需的 DateTime。传递 true 表示周日是一周的第一天，false 表示周一：
private DateTime getStartOfWeek(bool useSunday)
{
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
if(!useSunday)
dayOfWeek--;
if(dayOfWeek < 0)
{// day of week is Sunday and we want to use Monday as the start of the week
// Sunday is now the seventh day of the week
dayOfWeek = 6;
}
return now.AddDays(-1 * (double)dayOfWeek);
}
于 2008-09-01T15:19:08.770 回答
1
感谢您的示例。我需要始终使用“CurrentCulture”一周的第一天，对于一个数组，我需要知道确切的 Daynumber.. 所以这是我的第一个扩展：
public static class DateTimeExtensions
{
//http://stackoverflow.com/questions/38039/how-can-i-get-the-datetime-for-the-start-of-the-week
//http://stackoverflow.com/questions/1788508/calculate-date-with-monday-as-dayofweek1
public static DateTime StartOfWeek(this DateTime dt)
{
//difference in days
int diff = (int)dt.DayOfWeek - (int)CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek; //sunday=always0, monday=always1, etc.
//As a result we need to have day 0,1,2,3,4,5,6
if (diff < 0)
{
diff += 7;
}
return dt.AddDays(-1 * diff).Date;
}
public static int DayNoOfWeek(this DateTime dt)
{
//difference in days
int diff = (int)dt.DayOfWeek - (int)CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek; //sunday=always0, monday=always1, etc.
//As a result we need to have day 0,1,2,3,4,5,6
if (diff < 0)
{
diff += 7;
}
return diff + 1; //Make it 1..7
}
}
于 2010-05-21T15:14:25.223 回答
1
似乎还没有人正确回答这个问题。我会在这里粘贴我的解决方案，以防有人需要。无论一周的第一天是星期一还是星期日或其他什么，以下代码都有效。
public static class DateTimeExtension
{
public static DateTime GetFirstDayOfThisWeek(this DateTime d)
{
CultureInfo ci = System.Threading.Thread.CurrentThread.CurrentCulture;
var first = (int)ci.DateTimeFormat.FirstDayOfWeek;
var current = (int)d.DayOfWeek;
var result = first <= current ?
d.AddDays(-1 * (current - first)) :
d.AddDays(first - current - 7);
return result;
}
}
class Program
{
static void Main()
{
System.Threading.Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("en-US");
Console.WriteLine("Current culture set to en-US");
RunTests();
Console.WriteLine();
System.Threading.Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("da-DK");
Console.WriteLine("Current culture set to da-DK");
RunTests();
Console.ReadLine();
}
static void RunTests()
{
Console.WriteLine("Today {1}: {0}", DateTime.Today.Date.GetFirstDayOfThisWeek(), DateTime.Today.Date.ToString("yyyy-MM-dd"));
Console.WriteLine("Saturday 2013-03-02: {0}", new DateTime(2013, 3, 2).GetFirstDayOfThisWeek());
Console.WriteLine("Sunday 2013-03-03: {0}", new DateTime(2013, 3, 3).GetFirstDayOfThisWeek());
Console.WriteLine("Monday 2013-03-04: {0}", new DateTime(2013, 3, 4).GetFirstDayOfThisWeek());
}
}
于 2013-03-05T12:43:52.567 回答
1
C# 中的模数对 -1mod7 不好（应该是 6，c# 返回 -1）所以......“oneliner”解决方案看起来像这样:)
private static DateTime GetFirstDayOfWeek(DateTime date)
{
return date.AddDays(-(((int)date.DayOfWeek - 1) - (int)Math.Floor((double)((int)date.DayOfWeek - 1) / 7) * 7));
}
于 2015-12-18T10:16:49.500 回答
1
周末也一样（@Compile 这是答案的风格）：
public static DateTime EndOfWeek(this DateTime dt)
{
int diff = 7 - (int)dt.DayOfWeek;
diff = diff == 7 ? 0 : diff;
DateTime eow = dt.AddDays(diff).Date;
return new DateTime(eow.Year, eow.Month, eow.Day, 23, 59, 59, 999) { };
}
于 2017-04-28T15:46:04.730 回答
1
星期一做了，但星期天的逻辑类似。
public static DateTime GetStartOfWeekDate()
{
// Get today's date
DateTime today = DateTime.Today;
// Get the value for today. DayOfWeek is an enum with 0 being Sunday, 1 Monday, etc
var todayDayOfWeek = (int)today.DayOfWeek;
var dateStartOfWeek = today;
// If today is not Monday, then get the date for Monday
if (todayDayOfWeek != 1)
{
// How many days to get back to Monday from today
var daysToStartOfWeek = (todayDayOfWeek - 1);
// Subtract from today's date the number of days to get to Monday
dateStartOfWeek = today.AddDays(-daysToStartOfWeek);
}
return dateStartOfWeek;
}
于 2020-11-10T05:13:44.037 回答
0
您可以使用优秀的Umbrella 库：
using nVentive.Umbrella.Extensions.Calendar;
DateTime beginning = DateTime.Now.BeginningOfWeek();
但是，它们似乎确实将星期一存储为一周的第一天（请参阅属性）nVentive.Umbrella.Extensions.Calendar.DefaultDateTimeCalendarExtensions.WeekBeginsOn，因此以前的本地化解决方案要好一些。不幸的。
编辑：仔细研究这个问题，看起来 Umbrella 也可能适用于这个问题：
// Or DateTime.Now.PreviousDay(DayOfWeek.Monday)
DateTime monday = DateTime.Now.PreviousMonday();
DateTime sunday = DateTime.Now.PreviousSunday();
虽然值得注意的是，如果您在星期一要求前一个星期一，它会给您 7 天的回报。但是，如果您使用 ，这也是正确BeginningOfWeek的，这似乎是一个错误:(。
于 2008-09-01T16:34:07.140 回答
0
这将返回一周的开始和一周的结束日期：
private string[] GetWeekRange(DateTime dateToCheck)
{
string[] result = new string[2];
TimeSpan duration = new TimeSpan(0, 0, 0, 0); //One day
DateTime dateRangeBegin = dateToCheck;
DateTime dateRangeEnd = DateTime.Today.Add(duration);
dateRangeBegin = dateToCheck.AddDays(-(int)dateToCheck.DayOfWeek);
dateRangeEnd = dateToCheck.AddDays(6 - (int)dateToCheck.DayOfWeek);
result[0] = dateRangeBegin.Date.ToString();
result[1] = dateRangeEnd.Date.ToString();
return result;
}
我已经在我的博客ZamirsBlog上发布了用于计算周、月、季度和年的开始/结束的完整代码
于 2010-05-28T03:21:55.827 回答
0
namespace DateTimeExample
{
using System;
public static class DateTimeExtension
{
public static DateTime GetMonday(this DateTime time)
{
if (time.DayOfWeek != DayOfWeek.Monday)
return GetMonday(time.AddDays(-1)); //Recursive call
return time;
}
}
internal class Program
{
private static void Main()
{
Console.WriteLine(DateTime.Now.GetMonday());
Console.ReadLine();
}
}
}
于 2014-10-02T18:55:50.187 回答
0
这是几个答案的组合。它使用一种扩展方法，允许传入文化，如果没有传入，则使用当前文化。这将赋予它最大的灵活性和重用性。
/// <summary>
/// Gets the date of the first day of the week for the date.
/// </summary>
/// <param name="date">The date to be used</param>
/// <param name="cultureInfo">If none is provided, the current culture is used</param>
/// <returns>The date of the beggining of the week based on the culture specifed</returns>
public static DateTime StartOfWeek(this DateTime date, CultureInfo cultureInfo=null) =>
date.AddDays(-1 * (7 + (date.DayOfWeek - (cultureInfo??CultureInfo.CurrentCulture).DateTimeFormat.FirstDayOfWeek)) % 7).Date;
示例用法：
public static void TestFirstDayOfWeekExtension() {
DateTime date = DateTime.Now;
foreach(System.Globalization.CultureInfo culture in CultureInfo.GetCultures(CultureTypes.UserCustomCulture | CultureTypes.SpecificCultures)) {
Console.WriteLine($"{culture.EnglishName}: {date.ToShortDateString()} First Day of week: {date.StartOfWeek(culture).ToShortDateString()}");
}
}
于 2018-01-23T22:09:22.080 回答
0
如果您想要周六或周日或一周中的任何一天但不超过当前周（周六至周日），我让您了解这段代码。
public static DateTime GetDateInCurrentWeek(this DateTime date, DayOfWeek day)
{
var temp = date;
var limit = (int)date.DayOfWeek;
var returnDate = DateTime.MinValue;
if (date.DayOfWeek == day) return date;
for (int i = limit; i < 6; i++)
{
temp = temp.AddDays(1);
if (day == temp.DayOfWeek)
{
returnDate = temp;
break;
}
}
if (returnDate == DateTime.MinValue)
{
for (int i = limit; i > -1; i++)
{
date = date.AddDays(-1);
if (day == date.DayOfWeek)
{
returnDate = date;
break;
}
}
}
return returnDate;
}
于 2018-01-29T05:37:34.687 回答
0
我们喜欢单行：获取当前文化的一周的第一天和当天之间的差异，然后从当天减去天数
var weekStartDate = DateTime.Now.AddDays(-((int)now.DayOfWeek - (int)DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek));
于 2018-11-28T11:11:37.783 回答
0
继 Compile This' Answer 之后，使用以下方法获取一周中任何一天的日期：
public static DateTime GetDayOfWeek(DateTime dateTime, DayOfWeek dayOfWeek)
{
var monday = dateTime.Date.AddDays((7 + (dateTime.DayOfWeek - DayOfWeek.Monday) % 7) * -1);
var diff = dayOfWeek - DayOfWeek.Monday;
if (diff == -1)
{
diff = 6;
}
return monday.AddDays(diff);
}
于 2019-07-30T14:32:07.870 回答
0
通过这种方式计算，您可以选择一周中的哪一天表示新一周的开始（在我选择星期一的示例中）。
请注意，对星期一的一天进行此计算将给出当前的星期一，而不是前一个星期一。
//Replace with whatever input date you want
DateTime inputDate = DateTime.Now;
//For this example, weeks start on Monday
int startOfWeek = (int)DayOfWeek.Monday;
//Calculate the number of days it has been since the start of the week
int daysSinceStartOfWeek = ((int)inputDate.DayOfWeek + 7 - startOfWeek) % 7;
DateTime previousStartOfWeek = inputDate.AddDays(-daysSinceStartOfWeek);
于 2020-05-02T03:27:31.770 回答
-1
d = DateTime.Now;
int dayofweek =(int) d.DayOfWeek;
if (dayofweek != 0)
{
d = d.AddDays(1 - dayofweek);
}
else { d = d.AddDays(-6); }
于 2015-03-17T17:59:44.853 回答
-1
尝试创建一个使用递归的函数。您的 DateTime 对象是一个输入，函数返回一个新的 DateTime 对象，它代表一周的开始。
DateTime WeekBeginning(DateTime input)
{
do
{
if (input.DayOfWeek.ToString() == "Monday")
return input;
else
return WeekBeginning(input.AddDays(-1));
} while (input.DayOfWeek.ToString() == "Monday");
}
于 2020-03-27T18:25:49.750 回答
-1
我是这样做的：
DateTime.Now.Date.AddDays(-(DateTime.Now.Date.DayOfWeek == 0 ? 7 : (int)DateTime.Now.Date.DayOfWeek) + 1)
这段代码所做的只是从给定的日期时间中减去天数。
如果星期几为 0（星期日），则减去 7，否则减去星期几。
然后在上一行的结果中添加 1 天，即为该日期的星期一。
这样，您可以在最后使用数字（1）来获得所需的日期。
private static DateTime GetDay(DateTime date, int daysAmount = 1)
{
return date.Date.AddDays(-(date.Date.DayOfWeek == 0 ? 7 : (int)date.Date.DayOfWeek) + daysAmount);
}
如果你真的想使用 DayOfWeek 枚举，那么可以使用这样的东西......虽然我个人更喜欢上面的那个，因为我可以添加或减去任何天数。
private static DateTime GetDayOfWeek(DateTime date, DayOfWeek dayOfWeek = DayOfWeek.Monday)
{
return date.Date.AddDays(-(date.Date.DayOfWeek == 0 ? 7 : (int)date.Date.DayOfWeek) + (dayOfWeek == 0 ? 7 : (int)dayOfWeek));
}
于 2021-07-14T17:10:39.343 回答
-2
public static System.DateTime getstartweek()
{
System.DateTime dt = System.DateTime.Now;
System.DayOfWeek dmon = System.DayOfWeek.Monday;
int span = dt.DayOfWeek - dmon;
dt = dt.AddDays(-span);
return dt;
}
于 2009-12-02T01:50:22.467 回答