计算到下一个指定日期的剩余天数

Question

在您需要计算下一个 '计费日期'的场景中，如果日期(2日，25日等)已知，您如何计算距离下一次账单付款剩下的天数?

解释:

Tom的账单在每月4号生成

计算离下一次账单还有多少天的最好方法/逻辑是什么?例如，如果今天是本月28日，结果将是6 days left

我们知道:

票据生成日期已知

今天的日期是已知的

我已经做了什么:

int billingDay = 4; //The day the bill gets generated every month
DateTime today = DateTime.Today; //Today's date

我该如何继续计算下一个计费日期?

p。S:对不起，如果这听起来很蹩脚，我只是无法理解它

Answer 1

我想这行得通:

private int GetNumDaysToNextBillingDate(int billingDayOfMonth)
{
    DateTime today = DateTime.Today;
    if (today.Day <= billingDayOfMonth)
    {
        return (new DateTime(today.Year, today.Month, billingDayOfMonth) - today).Days;
    }
    else
    {
        var oneMonthFromToday = today.AddMonths(1);
        var billingDateNextMonth = 
            new DateTime(oneMonthFromToday.Year, 
            oneMonthFromToday.Month, billingDayOfMonth);
        return (billingDateNextMonth - today).Days;
    }
}

Answer 2

如何:

int billingDay = 4;
DateTime today = DateTime.UtcNow;
DateTime billing = today.Day >= billingDay
                   ? new DateTime(today.AddMonths(1).Year, today.AddMonths(1).Month, billingDay)
                   : new DateTime(today.Year, today.Month, billingDay);
TimeSpan left = billing - today;

Answer 3

这使用了一个循环，但由于它考虑了月份和年份的变化，因此不太容易出错:

    int DaysUntilBilling(int billingDay, DateTime referenceDate)
    {
        int count = 0;
        while (referenceDate.AddDays(count).Day != billingDay)
        {
            count++;               
        };
        return count;
    }

如果你总是使用今天的日期，你当然不需要传递DateTime作为参数，但这有助于测试不同的输入，你得到所需的输出:

int billingDay = 4;
DaysUntilBilling(billingDay, DateTime.Now); //26 (today is 9th Aug 2016)
DaysUntilBilling(billingDay, new DateTime(2016, 09, 03); //1
DaysUntilBilling(billingDay, new DateTime(2016, 09, 04); //0
DaysUntilBilling(billingDay, new DateTime(2016, 08, 05); //30
DaysUntilBilling(billingDay, new DateTime(2016, 12, 19); //16

Answer 4

此链接可能对您有所帮助:

https://msdn.microsoft.com/en-us/library/system.datetime.daysinmonth (v = vs.110) . aspx

你可以这样做:

        int daysUntilBill = 0;
        int billingDay = 4;
        DateTime today = DateTime.Today;
        if (billingDay > today.Day) {
            daysUntilBill = billingDay - today.Day;
        } else {
            int daysLeftInMonth = DateTime.DaysInMonth(today.Year, today.Month) - today.Day;
            daysUntilBill = billingDay + daysLeftInMonth;
        }

或者更简洁的

        int daysUntilBill = (billingDay >= today.Day) 
            ? billingDay - today.Day 
            : billingDay + DateTime.DaysInMonth(today.Year, today.Month) - today.Day;

这也可以很好地处理年的结尾，因为它没有试图绕过去。

Answer 5

首先，您需要确定当前日期是在开票日当天还是在开票日之前，以及是否只是减去当月的当前日期。否则，您必须确定下个月的下一个结算日期。

public int DaysToNextBill(int billingDay)
{
    var today = DateTime.Today;
    if(today.Day <= billingDay)
        return billingDay - today.Day;
    var nextMonth = today.AddMonth(1);
    var nextBillingDate = new DateTime(nextMonth.Year, nextMonth.Month, billingDay)
    return (nextBillingDate - today).Days;
}

唯一需要处理的是billingDay是否大于当前月或下个月的天数