Check if daylight savings is in effect?

问题:

How to check if in Denmark daylight time savings has taken effect, if so, then add 1 hour to my data, else not? I have a xml file:

<day = "1"
month = "5"
sunrise ="06:30"
sunset ="21:30"
/>

回答1:

Think you need convert this xml to DateTime and then use TimeZoneInfo class.

If Denmark your local time:

DateTime thisTime = DateTime.Now;
bool isDaylight = TimeZoneInfo.Local.IsDaylightSavingTime(thisTime);

Else you need to get Denmark TimeZone:

DateTime thisTime = DateTime.Now;
// get Denmark Standard Time zone - not sure about that
TimeZoneInfo tst = TimeZoneInfo.FindSystemTimeZoneById("Denmark Standard Time");
bool isDaylight = tst.IsDaylightSavingTime(thisTime);

回答2:

When I coded as above - for New-York, I found in the debugger that the time was set correctly (including DST)

TimeZoneInfo nyTimeZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");

DateTime nyTime = GetLocalDateTime(DateTime.UtcNow, nyTimeZone);

if (nyTimeZone.IsDaylightSavingTime(nyTime))
    nyTime = nyTime.AddHours(1);

public static DateTime GetLocalDateTime(DateTime utcDateTime, TimeZoneInfo timeZone)
    {

        utcDateTime = DateTime.SpecifyKind(utcDateTime, DateTimeKind.Utc);

        DateTime time = TimeZoneInfo.ConvertTime(utcDateTime, timeZone);

        return time;

    }

回答3:

You can use TimeZoneInfo.IsDaylightSavingTime

DateTime theDate = new DateTime(2012, 5, 1); // may 1st
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("Central European Standard Time");
bool isCurrentlyDaylightSavings = tzi.IsDaylightSavingTime(theDate);

回答4:

Here is a generic test and happy to be corrected if my math is incorrect. In my case I just needed to get the GMT offset for the timezone regardless of where it was in the world.

  int timezone;

  TimeZoneInfo localZone = TimeZoneInfo.Local;

  DateTime myTime = DateTime.Now;

  bool isDayLight = TimeZoneInfo.Local.IsDaylightSavingTime(myTime);

  if (isDayLight)
            timezone = Math.Abs(localZone.BaseUtcOffset.Hours) + 1;
  else
            timezone = Math.Abs(localZone.BaseUtcOffset.Hours);

  Debug.WriteLine("timezone is " + timezone);

I simply found the current time and if it was in Day Light Savings period added +1 to the GMT offset.

This works with Visual Studio Express 2013.

回答5:

You need to do two things:

1. call IsAmbiguous
2. List item IsDaylightSavingTime.

if (TimeZoneInfo.Local.IsAmbiguousTime(unclearDate) || TimeZoneInfo.Local.IsDaylightSavingTime(unclearDate)) Console.WriteLine("{0} may be daylight saving time in {1}.", unclearDate, TimeZoneInfo.Local.DisplayName);

https://msdn.microsoft.com/en-us/library/bb460642(v=vs.110).aspx

回答6:

this is my short solution which can be using in all timezones:

DateTime utcTime = DateTime.Parse("30.10.2018 18:21:34")
DateTime localtime = ConvertUTCToLocalTime(utcTime);


public static DateTime ConvertUTCToLocalTime(DateTime UTCTime)
{
    var localZone = TimeZone.CurrentTimeZone;
    var offset = localZone.GetUtcOffset(UTCTime);
    var localTime = UTCTime.AddHours(offset.Hours);
    return localTime;
}