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How to check if an hour exists in a specific Time Zone in .NET

During a Daylight Saving Time transition, the clock is moved forward, and so a specific hour will not exist in that specific day for that specific time zone.
Is there an easy way in .NET to find out if an hour exists or not for a time zone?
The only way I found was by trying to convert an hour to UTC, and check for an exception:
public bool IsValidTime(DateTime date, TimeZoneInfo tzi)
{
try
{
date = DateTime.SpecifyKind(date, DateTimeKind.Unspecified);
TimeZoneInfo.ConvertTimeToUtc(date, tzi);
return true;
}
catch
{
return false;
}
}
And so running something like this will return false:
var date = new DateTime(2020, 3, 8);
var tzi = TimeZoneInfo.FindSystemTimeZoneById("Cuba Standard Time");
var isValid = IsValidTime(date, tzi);
Is there any built in way of doing this, that is less messy?

You can use IsInvalidTime method of TimeZoneInfo.
From Microsoft : https://learn.microsoft.com/en-us/dotnet/api/system.timezoneinfo.isinvalidtime?view=netframework-4.6.2
Example: In the Pacific Time zone, daylight saving time begins at 2:00 A.M. on April 2, 2006. The following code passes the time at one-minute intervals from 1:59 A.M. on April 2, 2006, to 3:01 A.M. on April 2, 2006, to the IsInvalidTime method of a TimeZoneInfo object that represents the Pacific Time zone. The console output indicates that all times from 2:00 A.M. on April 2, 2006, to 2:59 A.M. on April 2, 2006, are invalid.
// Specify DateTimeKind in Date constructor
DateTime baseTime = new DateTime(2007, 3, 11, 1, 59, 0, DateTimeKind.Unspecified);
DateTime newTime;
// Get Pacific Standard Time zone
TimeZoneInfo pstZone = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");
// List possible invalid times for a 63-minute interval, from 1:59 AM to 3:01 AM
for (int ctr = 0; ctr < 63; ctr++)
{
// Because of assignment, newTime.Kind is also DateTimeKind.Unspecified
newTime = baseTime.AddMinutes(ctr);
Console.WriteLine("{0} is invalid: {1}", newTime, pstZone.IsInvalidTime(newTime));
}

Converting multiple timezone to local time

I'm saving date time in CST timezone,how to change the CST date time to local time.
Ex:
In DB,
Date time is 2013-01-21 06:50:00 and its timezone is CST.This Date Time should be converted into local current time.

Save them as UTC time and then convert them to local time when loading to the UI.

A sample code would be like
using System;
public class Example
{
public static void Main()
{
DateTime date1 = new DateTime(2010, 3, 14, 2, 30, 0, DateTimeKind.Local);
Console.WriteLine("Invalid time: {0}",
TimeZoneInfo.Local.IsInvalidTime(date1));
DateTime utcDate1 = date1.ToUniversalTime();
DateTime date2 = utcDate1.ToLocalTime();
Console.WriteLine("{0} --> {1}", date1, date2);
}
}
// The example displays the following output:
// Invalid time: True
// 3/14/2010 2:30:00 AM --> 3/14/2010 3:30:00 AM
Hope this helps

Check if daylight savings is in effect?

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"
/>

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);

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;
}

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);

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.

You need to do two things:
call IsAmbiguous
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

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;
}

Important
myDateTime.IsDaylightSavingTime DOES return the proper value... but... it is accurate down to at least the hour of the day, just passing the date alone isn't enough.
For instance this year (2019) 3/10/2019 02:00:00 passed as myDateTime will return false, but 3/10/2019 03:00:00 will return true.

Based on other codes provided above, I made a complete code to run and make tests. The variable cityTz is receiving an IANA timezone name example. IANA timezone pattern is used in Mac and Linux (Windows uses different timezone style). In 2020, daylight-saving (DST) in New York ends on November 01. If you test the code below, the return will be FALSE, because "theDate" is November 02, the next day after the end of DST. But if you change the line commented and set theDate to November 01 (last DST date in NY), the return will be TRUE.
You can compile this program in Mac or Linux terminal typing:
csc testDST.cs
To run your program:
mono testDST.exe
Complete code:
using System;
using System.Collections.Generic;
using System.Linq;
class Program{
static void Main(string[] args)
{
string cityTz;
//cityTz = "America/Sao_Paulo";
cityTz = "America/New_York";
//DateTime theDate = new DateTime(2020, 11, 1); //returns TRUE
DateTime theDate = new DateTime(2020, 11, 2); //returns FALSE
Console.WriteLine("Data: "+theDate);
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById(cityTz);
bool isDaylight = tzi.IsDaylightSavingTime(theDate);
Console.WriteLine("isDaylight this date in "+ cityTz +"?: "+ isDaylight);
}
}

C# DateTime to UTC Time without changing the time

How would I convert a preexisting datetime to UTC time without changing the actual time.
Example:
DateTime dateTime = GetSomeDateTime(); // dateTime here is 3pm
dateTime.ToUtcDateTime() // datetime should still be 3pm

6/1/2011 4:08:40 PM Local
6/1/2011 4:08:40 PM Utc
from
DateTime dt = DateTime.Now;
Console.WriteLine("{0} {1}", dt, dt.Kind);
DateTime ut = DateTime.SpecifyKind(dt, DateTimeKind.Utc);
Console.WriteLine("{0} {1}", ut, ut.Kind);

Use the DateTime.SpecifyKind static method.
Creates a new DateTime object that has the same number of ticks as the specified DateTime, but is designated as either local time, Coordinated Universal Time (UTC), or neither, as indicated by the specified DateTimeKind value.
Example:
DateTime dateTime = DateTime.Now;
DateTime other = DateTime.SpecifyKind(dateTime, DateTimeKind.Utc);
Console.WriteLine(dateTime + " " + dateTime.Kind); // 6/1/2011 4:14:54 PM Local
Console.WriteLine(other + " " + other.Kind); // 6/1/2011 4:14:54 PM Utc

You can use the overloaded constructor of DateTime:
DateTime utcDateTime = new DateTime(dateTime.Year, dateTime.Month, dateTime.Day, dateTime.Hour, dateTime.Minute, dateTime.Second, DateTimeKind.Utc);

Use the DateTime.ToUniversalTime method.

Convert UTC DateTime to another Time Zone

I have a UTC DateTime value coming from a database record. I also have a user-specified time zone (an instance of TimeZoneInfo). How do I convert that UTC DateTime to the user's local time zone? Also, how do I determine if the user-specified time zone is currently observing DST? I'm using .NET 3.5.
Thanks,
Mark

The best way to do this is simply to use TimeZoneInfo.ConvertTimeFromUtc.
// you said you had these already
DateTime utc = new DateTime(2014, 6, 4, 12, 34, 0);
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");
// it's a simple one-liner
DateTime pacific = TimeZoneInfo.ConvertTimeFromUtc(utc, tzi);
The only catch is that the incoming DateTime value may not have the DateTimeKind.Local kind. It must either be Utc, or Unspecified.

You can use a dedicated function within TimeZoneInfo if you want to convert a DateTimeOffset into another DateTimeOffset:
DateTimeOffset newTime = TimeZoneInfo.ConvertTime(
DateTimeOffset.UtcNow,
TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time")
);

Have a look at the DateTimeOffset structure:
// user-specified time zone
TimeZoneInfo southPole =
TimeZoneInfo.FindSystemTimeZoneById("Antarctica/South Pole Standard Time");
// an UTC DateTime
DateTime utcTime = new DateTime(2007, 07, 12, 06, 32, 00, DateTimeKind.Utc);
// DateTime with offset
DateTimeOffset dateAndOffset =
new DateTimeOffset(utcTime, southPole.GetUtcOffset(utcTime));
Console.WriteLine(dateAndOffset);
For DST see the TimeZoneInfo.IsDaylightSavingTime method.
bool isDst = southpole.IsDaylightSavingTime(DateTime.UtcNow);

The Antartica answer only works for the timezones matching UTC. I'm quite traumatized with this DateTimeOffset function and after hours of trial and error, I've managed to produce a practical conversion extension function that works with all timezones.
static public class DateTimeFunctions
{
static public DateTimeOffset ConvertUtcTimeToTimeZone(this DateTime dateTime, string toTimeZoneDesc)
{
if (dateTime.Kind != DateTimeKind.Utc) throw new Exception("dateTime needs to have Kind property set to Utc");
var toUtcOffset = TimeZoneInfo.FindSystemTimeZoneById(toTimeZoneDesc).GetUtcOffset(dateTime);
var convertedTime = DateTime.SpecifyKind(dateTime.Add(toUtcOffset), DateTimeKind.Unspecified);
return new DateTimeOffset(convertedTime, toUtcOffset);
}
}
Example:
var currentTimeInPacificTime = DateTime.UtcNow.ConvertUtcTimeToTimeZone("Pacific Standard Time");

Here's another gotcha: If you're running your code on a Linux server, you need to use the Linux system for timezone names. For example, "Central Standard Time" would be "America/Chicago". The tz list is here: https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
Here's an example with the isWindows switch:
public static class DateTimeHelper
{
public static string ConvertUtcToCst(this string dateTimeString)
{
if (string.IsNullOrWhiteSpace(dateTimeString))
{
return string.Empty;
}
if (DateTime.TryParse(dateTimeString, out DateTime outputDateTime))
{
try
{
var isWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
TimeZoneInfo cstZone = null;
if (isWindows)
{
cstZone = TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time");
}
else
{
cstZone = TimeZoneInfo.FindSystemTimeZoneById("America/Chicago");
}
var cstDateTime = TimeZoneInfo.ConvertTimeFromUtc(outputDateTime, cstZone);
return cstDateTime.ToString();
}
catch (TimeZoneNotFoundException)
{
return "The registry does not define the Central Standard Time zone.";
}
catch (InvalidTimeZoneException)
{
return "Registry data on the Central Standard Time zone has been corrupted.";
}
catch (Exception ex)
{
return $"Error :: {ex.Message} :: {ex.ToString()}";
}
}
return string.Empty;
}
}

// TO get Currrent Time in current Time Zone of your System
var dt = DateTime.Now;
Console.WriteLine(dt);
// Display Time Zone of your System
Console.WriteLine(TimeZoneInfo.Local);
// Convert Current Date Time to UTC Date Time
var utc = TimeZoneInfo.ConvertTimeToUtc(dt, TimeZoneInfo.Local);
Console.WriteLine(utc);
// Convert UTC Time to Current Time Zone
DateTime pacific = TimeZoneInfo.ConvertTimeFromUtc(utc, TimeZoneInfo.Local);
Console.WriteLine(pacific);
Console.ReadLine();