Question

我现在不在我的代码前面，但我真的不认为我需要它来提出这个问题。所以我有一个倒计时器，每18小时关闭一次，然后重置。计时器检查当前DateTime.Now并根据需要调整倒数计时器。我有一个问题，试图考虑到夏令时可以追溯到一小时后，因为;例如，2017年11月5日凌晨2点这个过去的事件可以追溯到凌晨1点，但是当我DateTime.IsDaylightSavingTime()时，它告诉我即使夏令时刚刚结束也是假的。这使得我的计时器又回来了一个小时，因为它认为夏令时仍然没有发生在那一小时的时间段内。我该如何解决这个问题？

Answer 1

我会使用DateTime.UtcNow你不会遇到夏令时问题

Answer 2

如果由于某种原因您真的需要使用当地时间，那么您应该提前计算DST更改（事先安排下一个事件）。

TimeZoneInfo.GetAdjustmentRules（）应该可以帮助您获得下一次DST调整的时间和增量。

以下是进行上调调整的代码：

    public static DateTime? GetNextAdjustmentDate(TimeZoneInfo timeZoneInfo)
    {
        var adjustments = timeZoneInfo.GetAdjustmentRules();

        if (adjustments.Length == 0)
        {
            return null;
        }

        int year = DateTime.UtcNow.Year;
        TimeZoneInfo.AdjustmentRule adjustment = null;
        foreach (TimeZoneInfo.AdjustmentRule adjustment1 in adjustments)
        {
            // Determine if this adjustment rule covers year desired 
            if (adjustment1.DateStart.Year <= year && adjustment1.DateEnd.Year >= year)
                adjustment = adjustment1;
        }
        if (adjustment == null)
            return null;

        //TimeZoneInfo.TransitionTime startTransition, endTransition;

        DateTime dstStart = GetCurrentYearAdjustmentDate(adjustment.DaylightTransitionStart);
        DateTime dstEnd = GetCurrentYearAdjustmentDate(adjustment.DaylightTransitionEnd);


        if (dstStart >= DateTime.UtcNow.Date)
            return dstStart;
        if (dstEnd >= DateTime.UtcNow.Date)
            return dstEnd;
        return null;
    }

    private static DateTime GetCurrentYearAdjustmentDate(TimeZoneInfo.TransitionTime transitionTime)
    {
        int year = DateTime.UtcNow.Year;

        if (transitionTime.IsFixedDateRule)
            return new DateTime(year, transitionTime.Month, transitionTime.Day);
        else
        {
            // For non-fixed date rules, get local calendar
            System.Globalization.Calendar cal = CultureInfo.CurrentCulture.Calendar;
            // Get first day of week for transition 
            // For example, the 3rd week starts no earlier than the 15th of the month 
            int startOfWeek = transitionTime.Week * 7 - 6;
            // What day of the week does the month start on? 
            int firstDayOfWeek = (int)cal.GetDayOfWeek(new DateTime(year, transitionTime.Month, 1));
            // Determine how much start date has to be adjusted 
            int transitionDay;
            int changeDayOfWeek = (int)transitionTime.DayOfWeek;

            if (firstDayOfWeek <= changeDayOfWeek)
                transitionDay = startOfWeek + (changeDayOfWeek - firstDayOfWeek);
            else
                transitionDay = startOfWeek + (7 - firstDayOfWeek + changeDayOfWeek);

            // Adjust for months with no fifth week 
            if (transitionDay > cal.GetDaysInMonth(year, transitionTime.Month))
                transitionDay -= 7;

            return new DateTime(year, transitionTime.Month, transitionDay);
        }
    }

您需要添加更多代码才能检索并应用调整增量。

嗯 - 现在，当你看到所有需要完成的艰苦工作（而不是维护并确保无bug）时，你可能想要解决你的问题以便能够使用UTC < /强>

我怎么知道夏令时刚刚过了一小时就消失了？

2 个答案: