根据当前系统日期求出本周，本月，本年，上周，上月，上年的第一天
?//今天?DateTime.Now.Date.ToShortDateString();
//昨天，就是今天的日期減一
?DateTime.Now.AddDays(-1).ToShortDateString();
//明天，同理，加一?DateTime.Now.AddDays(1).ToShortDateString();/
/本周(要知道本周的第一天就得先知道今天是星期幾，從而得知本周的第一天就是幾天前的那一天，要注意的是這里的每一周是從周日始至周六止?DateTime.Now.AddDays(Convert.ToDouble((0-Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString(); DateTime.Now.AddDays(Convert.ToDouble((6-Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
//如果你還不明白，再看一下中文顯示星期幾的方法就應該懂了
//由于DayOfWeek返回的是數(shù)字的星期幾，我們要把它轉換成漢字方便我們閱讀，有些人可能會用switch來一個一個地對照，其實不用那么麻煩的
string[] Day=?newstring[] {?"星期日","星期一","星期二","星期三","星期四","星期五","星期六"?}; Day[Convert.ToInt16(DateTime.Now.DayOfWeek)];/
/上周，同理，一個周是7天，上周就是本周再減去7天，下周也是一樣
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();
//下周?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();
//本月,很多人都會說本月的第一天嘛肯定是1號，最后一天就是下個月一號再減一天。當然這是對的
?//一般的寫法
?DateTime.Now.Year.ToString()+?DateTime.Now.Month.ToString()+?"1";
//第一天?DateTime.Parse(DateTime.Now.Year.ToString()+?DateTime.Now.Month.ToString()+"1").AddMonths(1).AddDays(-1).ToShortDateString();
//最后一天?//巧用C#里ToString的字符格式化更簡便
DateTime.Now.ToString("yyyy-MM-01"); DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).AddDays(-1).ToShortDateString();
?//上個月，減去一個月份
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(-1).ToShortDateString(); DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//下個月，加去一個月份
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).ToShortDateString(); DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(2).AddDays(-1).ToShortDateString();
//7天后?DateTime.Now.Date.ToShortDateString(); DateTime.Now.AddDays(7).ToShortDateString();
//7天前?DateTime.Now.AddDays(-7).ToShortDateString(); DateTime.Now.Date.ToShortDateString();
//本年度，用ToString的字符格式化我們也很容易地算出本年度的第一天和最后一天
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).ToShortDateString(); DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).AddDays(-1).ToShortDateString();
//上年度，不用再解釋了吧
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(-1).ToShortDateString(); DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddDays(-1).ToShortDateString();
//下年度
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).ToShortDateString(); DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(2).AddDays(-1).ToShortDateString();
//本季度，很多人都會覺得這里難點，需要寫個長長的過程來判斷。其實不用的，我們都知道一年四個季度，一個季度三個月
//首先我們先把日期推到本季度第一個月，然后這個月的第一天就是本季度的第一天了
?DateTime.Now.AddMonths(0-?((DateTime.Now.Month-?1)%?3)).ToString("yyyy-MM-01");
//同理，本季度的最后一天就是下季度的第一天減一
DateTime.Parse(DateTime.Now.AddMonths(3-?((DateTime.Now.Month-?1)%?3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//下季度，相信你們都知道了。。。。收工
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();
?//上季度
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();
?
?
?
//定義變量?
??????? private static DateTime currentDateTime;??????? //當前時間
??????? private static DateTime lastDateTime;?????????? //昨天時間
??????? private static DateTime nextDateTime;?????????? //明天時間
??????? private static int currentDayOfWeek;??????????? //今天星期幾
??????? private static int lastDayOfWeek;?????????????? //昨天星期幾
??????? private static int nextDayOfWeek;?????????????? //明天星期幾
??????? private static DateTime currentStartWeek;?????? //本周周一
??????? private static DateTime currentEndWeek;???????? //本周周日
??????? private static DateTime currentStartMonth;????? //本月月初
??????? private static DateTime currentEndMonth;??????? //本月月末
??????? private static DateTime currentStartQuarter;??? //本季度初
??????? private static DateTime currentEndQuarter;????? //本季度末
??????? private static DateTime currentStartYear;?????? //今年年初
??????? private static DateTime currentEndYear;???????? //今年年末
??????? private static DateTime lastStartWeek;????????? //上周周一
??????? private static DateTime lastEndWeek;??????????? //上周周日
??????? private static DateTime lastStartMonth;???????? //上月月初
??????? private static DateTime lastEndMonth;?????????? //上月月末
??????? private static DateTime lastStartQuarter;?????? //上季度初
??????? private static DateTime lastEndQuarter;???????? //上季度末
??????? private static DateTime lastStartYear;????????? //去年年初
??????? private static DateTime lastEndYear;??????????? //去年年末
??????? private static DateTime nextStartWeek;????????? //下周周一
??????? private static DateTime nextEndWeek;??????????? //下周周日
??????? private static DateTime nextStartMonth;???????? //下月月初
??????? private static DateTime nextEndMonth;?????????? //下月月末
??????? private static DateTime nextStartQuarter;?????? //下季度初
??????? private static DateTime nextEndQuarter;???????? //下季度末
??????? private static DateTime nextStartYear;????????? //明年年初
??????? private static DateTime nextEndYear;??????????? //明年年末
?
//計算變量
??????????? currentDateTime = DateTime.Now;???????????????? //當前時間
??????????? lastDateTime = DateTime.Now.AddDays(-1);??????? //昨天時間
??????????? nextDateTime = DateTime.Now.AddDays(1);???????? //明天時間
??????????? currentDayOfWeek = Convert.ToInt32(currentDateTime.DayOfWeek.ToString("d"));??? //今天星期幾
??????????? currentDayOfWeek = Convert.ToInt32(lastDateTime.DayOfWeek.ToString("d"));?????? //昨天星期幾
??????????? currentDayOfWeek = Convert.ToInt32(nextDateTime.DayOfWeek.ToString("d"));?????? //明天星期幾
??????????? currentStartWeek = currentDateTime.AddDays(1 - ((currentDayOfWeek == 0) ? 7 : currentDayOfWeek));?? //本周周一
??????????? currentEndWeek = currentStartWeek.AddDays(6);?????????????????????????????????????????????????????? //本周周日???????????
??????????? lastStartWeek = currentStartWeek.AddDays(-7);?????? //上周周一
??????????? lastEndWeek = currentEndWeek.AddDays(-7);?????????? //上周周日
??????????? nextStartWeek = currentStartWeek.AddDays(7);??????? //下周周一
??????????? nextEndWeek = currentEndWeek.AddDays(7);??????????? //下周周日
??????????? currentStartMonth = currentDateTime.AddDays(1 - currentDateTime.Day);?? //本月月初
??????????? currentEndMonth = currentStartMonth.AddMonths(1).AddDays(-1);?????????? //本月月末
??????????? lastStartMonth = currentStartMonth.AddMonths(-1);?????? //上月月初
??????????? lastEndMonth = currentStartMonth.AddDays(-1);?????????? //上月月末
??????????? nextStartMonth = currentEndMonth.AddDays(1);??????????? //下月月初
??????????? nextEndMonth = nextStartMonth.AddMonths(1).AddDays(-1); //下月月末
??????????? currentStartQuarter = currentDateTime.AddMonths(0 - (currentDateTime.Month - 1) % 3).AddDays(1 - currentDateTime.Day);? //本季度初
??????????? currentEndQuarter = currentStartQuarter.AddMonths(3).AddDays(-1);????????????????????????????????????????????????????? //本季度末
??????????? lastStartQuarter = currentStartQuarter.AddMonths(-3);?????????? //上季度初
??????????? lastEndQuarter = currentStartQuarter.AddDays(-1);?????????????? //上季度末
??????????? nextStartQuarter = currentEndQuarter.AddDays(1);??????????????? //下季度初
??????????? nextEndQuarter = nextStartQuarter.AddMonths(3).AddDays(-1);???? //下季度末
??????????? //年度運算
??????????? currentStartYear = new DateTime(currentDateTime.Year, 1, 1);? //今年年初
??????????? currentEndYear = new DateTime(currentDateTime.Year, 12, 31);? //今年年末
??????????? lastStartYear = currentStartYear.AddYears(-1);? //去年年初
??????????? lastEndYear = currentEndYear.AddYears(-1);????? //去年年末
??????????? nextStartYear = currentStartYear.AddYears(1);?? //明年年初
??????????? nextEndYear = currentEndYear.AddYears(1);?????? //明年年末
?
??????? /// <summary>
??????? /// 返回星期幾字符串函數(shù)
??????? /// </summary>
??????? /// <param name="myDateTime"></param>
??????? /// <returns></returns>
??????? private string GetWeekDayName(DateTime myDateTime)
??????? {
??????????? string week = "";
??????????? //獲取當前日期是星期幾
??????????? string dt = myDateTime.DayOfWeek.ToString();
??????????? //根據(jù)取得的星期英文單詞返回漢字
??????????? switch (dt)
??????????? {
??????????????? case "Monday":
??????????????????? week = "星期一";
??????????????????? break;
??????????????? case "Tuesday":
??????????????????? week = "星期二";
??????????????????? break;
??????????????? case "Wednesday":
??????????????????? week = "星期三";
??????????????????? break;
??????????????? case "Thursday":
??????????????????? week = "星期四";
??????????????????? break;
??????????????? case "Friday":
??????????????????? week = "星期五";
??????????????????? break;
??????????????? case "Saturday":
??????????????????? week = "星期六";
??????????????????? break;
??????????????? case "Sunday":
??????????????????? week = "星期日";
??????????????????? break;
??????????? }
??????????? return week;
??????? }
?
//今天 ??DateTime.Now.Date.ToShortDateString(); ??
//昨天，就是今天的日期減一 ??
DateTime.Now.AddDays(-1).ToShortDateString(); ??
//明天，同理，加一 ??
DateTime.Now.AddDays(1).ToShortDateString(); ??
??
//本周(要知道本周的第一天就得先知道今天是星期幾，從而得知本周的第一天就是幾天前的那一天，要注意的是這里的每一周是從周日始至周六止 ??
DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString(); ??
DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString(); ??
//如果你還不明白，再看一下中文顯示星期幾的方法就應該懂了 ??
//由于DayOfWeek返回的是數(shù)字的星期幾，我們要把它轉換成漢字方便我們閱讀，有些人可能會用switch來一個一個地對照，其實不用那么麻煩的 ? ? ? ? ? ? ? ??
string[] Day = new string[] { "星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六" }; ??
Day[Convert.ToInt16(DateTime.Now.DayOfWeek)]; ??
??
//上周，同理，一個周是7天，上周就是本周再減去7天，下周也是一樣 ??
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(); ??
//下周 ??
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(); ??
//本月,很多人都會說本月的第一天嘛肯定是1號，最后一天就是下個月一號再減一天。當然這是對的 ??
//一般的寫法 ??
DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1"; //第一天 ??
DateTime.Parse(DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1").AddMonths(1).AddDays(-1).ToShortDateString();//最后一天 ??
??
//巧用C#里ToString的字符格式化更簡便 ??
DateTime.Now.ToString("yyyy-MM-01"); ??
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).AddDays(-1).ToShortDateString(); ??
??
//上個月，減去一個月份 ??
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(-1).ToShortDateString(); ??
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString(); ??
//下個月，加去一個月份 ??
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).ToShortDateString(); ??
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(2).AddDays(-1).ToShortDateString(); ??
//7天后 ??
DateTime.Now.Date.ToShortDateString(); ??
DateTime.Now.AddDays(7).ToShortDateString(); ??
//7天前 ??
DateTime.Now.AddDays(-7).ToShortDateString(); ??
DateTime.Now.Date.ToShortDateString(); ??
??
//本年度，用ToString的字符格式化我們也很容易地算出本年度的第一天和最后一天 ??
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).ToShortDateString(); ??
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).AddDays(-1).ToShortDateString(); ??
//上年度，不用再解釋了吧 ??
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(-1).ToShortDateString(); ??
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddDays(-1).ToShortDateString(); ??
//下年度 ??
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).ToShortDateString(); ??
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(2).AddDays(-1).ToShortDateString(); ??
??
//本季度，很多人都會覺得這里難點，需要寫個長長的過程來判斷。其實不用的，我們都知道一年四個季度，一個季度三個月 ??
//首先我們先把日期推到本季度第一個月，然后這個月的第一天就是本季度的第一天了 ??
DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01"); ??
//同理，本季度的最后一天就是下季度的第一天減一 ??
DateTime.Parse(DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString(); ??
//下季度，相信你們都知道了。。。。收工 ??
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(); ??
//上季度 ??
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(); ?
?
原文：http://blog.csdn.net/hefeng_aspnet/article/details/6616650
轉載于:https://www.cnblogs.com/Percy_Lee/p/5308038.html
總結
以上是生活随笔為你收集整理的根据当前系统日期求出本周，本月，本年，上周，上月，上年的第一天的全部內容，希望文章能夠幫你解決所遇到的問題。
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