如何在c#中计算两个日期之间的月差?
c#中是否有相当于VB的DateDiff()方法。我需要找出相隔数年的两个日期之间的月差。文档说我可以像这样使用TimeSpan:
TimeSpan ts = date1 - date2;
但这里的数据是以天为单位的。我不想把这个数字除以30,因为不是每个月都是30天,而且两个操作数的值相差很大,所以我担心除以30可能会得到错误的值。
有什么建议吗?
如何在c#中计算两个日期之间的月差?
c#中是否有相当于VB的DateDiff()方法。我需要找出相隔数年的两个日期之间的月差。文档说我可以像这样使用TimeSpan:
TimeSpan ts = date1 - date2;
但这里的数据是以天为单位的。我不想把这个数字除以30,因为不是每个月都是30天,而且两个操作数的值相差很大,所以我担心除以30可能会得到错误的值。
有什么建议吗?
当前回答
要获得月份的差异(包括开始和结束),而不考虑日期:
DateTime start = new DateTime(2013, 1, 1);
DateTime end = new DateTime(2014, 2, 1);
var diffMonths = (end.Month + end.Year * 12) - (start.Month + start.Year * 12);
其他回答
疯狂的方法,计算所有的日子,超级精确
Helper类:
public class DaysInMonth
{
public int Days { get; set; }
public int Month { get; set; }
public int Year { get; set; }
public bool Full { get; set; }
}
功能:
public static List<DaysInMonth> MonthsDelta(DateTime start, DateTime end)
{
var dates = Enumerable.Range(0, 1 + end.Subtract(start).Days)
.Select(offset => start.AddDays(offset))
.ToArray();
DateTime? prev = null;
int days = 0;
List < DaysInMonth > list = new List<DaysInMonth>();
foreach (DateTime date in dates)
{
if (prev != null)
{
if(date.Month!=prev.GetValueOrDefault().Month)
{
DaysInMonth daysInMonth = new DaysInMonth();
daysInMonth.Days = days;
daysInMonth.Month = prev.GetValueOrDefault().Month;
daysInMonth.Year = prev.GetValueOrDefault().Year;
daysInMonth.Full = DateTime.DaysInMonth(daysInMonth.Year, daysInMonth.Month) == daysInMonth.Days;
list.Add(daysInMonth);
days = 0;
}
}
days++;
prev = date;
}
//------------------ add last
if (days > 0)
{
DaysInMonth daysInMonth = new DaysInMonth();
daysInMonth.Days = days;
daysInMonth.Month = prev.GetValueOrDefault().Month;
daysInMonth.Year = prev.GetValueOrDefault().Year;
daysInMonth.Full = DateTime.DaysInMonth(daysInMonth.Year, daysInMonth.Month) == daysInMonth.Days;
list.Add(daysInMonth);
}
return list;
}
扩展的Kirks结构与ToString(格式)和持续时间(长ms)
public struct DateTimeSpan
{
private readonly int years;
private readonly int months;
private readonly int days;
private readonly int hours;
private readonly int minutes;
private readonly int seconds;
private readonly int milliseconds;
public DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds, int milliseconds)
{
this.years = years;
this.months = months;
this.days = days;
this.hours = hours;
this.minutes = minutes;
this.seconds = seconds;
this.milliseconds = milliseconds;
}
public int Years { get { return years; } }
public int Months { get { return months; } }
public int Days { get { return days; } }
public int Hours { get { return hours; } }
public int Minutes { get { return minutes; } }
public int Seconds { get { return seconds; } }
public int Milliseconds { get { return milliseconds; } }
enum Phase { Years, Months, Days, Done }
public string ToString(string format)
{
format = format.Replace("YYYY", Years.ToString());
format = format.Replace("MM", Months.ToString());
format = format.Replace("DD", Days.ToString());
format = format.Replace("hh", Hours.ToString());
format = format.Replace("mm", Minutes.ToString());
format = format.Replace("ss", Seconds.ToString());
format = format.Replace("ms", Milliseconds.ToString());
return format;
}
public static DateTimeSpan Duration(long ms)
{
DateTime dt = new DateTime();
return CompareDates(dt, dt.AddMilliseconds(ms));
}
public static DateTimeSpan CompareDates(DateTime date1, DateTime date2)
{
if (date2 < date1)
{
var sub = date1;
date1 = date2;
date2 = sub;
}
DateTime current = date1;
int years = 0;
int months = 0;
int days = 0;
Phase phase = Phase.Years;
DateTimeSpan span = new DateTimeSpan();
while (phase != Phase.Done)
{
switch (phase)
{
case Phase.Years:
if (current.AddYears(years + 1) > date2)
{
phase = Phase.Months;
current = current.AddYears(years);
}
else
{
years++;
}
break;
case Phase.Months:
if (current.AddMonths(months + 1) > date2)
{
phase = Phase.Days;
current = current.AddMonths(months);
}
else
{
months++;
}
break;
case Phase.Days:
if (current.AddDays(days + 1) > date2)
{
current = current.AddDays(days);
var timespan = date2 - current;
span = new DateTimeSpan(years, months, days, timespan.Hours, timespan.Minutes, timespan.Seconds, timespan.Milliseconds);
phase = Phase.Done;
}
else
{
days++;
}
break;
}
}
return span;
}
}
我们是这样做的:
public static int MonthDiff(DateTime date1, DateTime date2)
{
if (date1.Month < date2.Month)
{
return (date2.Year - date1.Year) * 12 + date2.Month - date1.Month;
}
else
{
return (date2.Year - date1.Year - 1) * 12 + date2.Month - date1.Month + 12;
}
}
假设这个月的日期不相关(即2011.1.1和2010.12.31之间的差为1),date1 > date2为正值,date2 > date1为负值
((date1.Year - date2.Year) * 12) + date1.Month - date2.Month
或者,假设你想要两个日期之间的“平均月”的大致数字,下面的方法应该适用于所有日期,但日期差异非常大。
date1.Subtract(date2).Days / (365.25 / 12)
注意,如果您要使用后一种解决方案,那么您的单元测试应该声明应用程序设计使用的最宽日期范围,并相应地验证计算结果。
更新(感谢Gary)
如果使用“平均月份”方法,“每年平均天数”的更准确数字是365.2425。
有3种情况:同一年,前一年和其他年份。
如果日期不重要的话……
public int GetTotalNumberOfMonths(DateTime start, DateTime end)
{
// work with dates in the right order
if (start > end)
{
var swapper = start;
start = end;
end = swapper;
}
switch (end.Year - start.Year)
{
case 0: // Same year
return end.Month - start.Month;
case 1: // last year
return (12 - start.Month) + end.Month;
default:
return 12 * (3 - (end.Year - start.Year)) + (12 - start.Month) + end.Month;
}
}