Develop Reference

Convert System.DateTime to NodaTime.ZonedDateTime

I have a System.DateTime which is already in a specific timezone but does not specify a DateTime.Kind, and a string that represents an IANA timezone. I want to convert this to a NodaTime.ZonedDateTime.
For example:
var original = new DateTime(2016, 1, 1, 12, 0, 0);
var timezone = "America/Chicago";
I want a ZonedDateTime that represents 01/01/2016 - 12PM in Chicago time. How do I do this?

If I understand you correctly, you want to take a standard DateTime with a known time in Chicago and get a ZonedDateTime representing this Date + Time + Time Zone, correct?
If so, I believe this will do it. The intermediate conversion from DateTime to LocalDateTime might not be necessary if you can construct it directly.
var dotNetDateTime = new DateTime(2016, 1, 1, 12, 0, 0);
var localDate = LocalDateTime.FromDateTime(dotNetDateTime);
var chicagoTime = DateTimeZoneProviders.Tzdb["America/Chicago"];
var chicagoZonedDateTime = chicagoTime.AtStrictly(localDate); // Will contain 2016 01 01 noon
// now you can convert to time in Los Angeles
var laTime = DateTimeZoneProviders.Tzdb["America/Los_Angeles"];
var laZonedDateTime = chicagoZonedDateTime.WithZone(laTime); // will contain 2016 01 01 10am

c# DataTime: Assume EST convert to GTM

I have a server running in New York that saves a DateTime into the database in local time.
I then have a client application running in GMT timezone that needs to save down a DateTime in the same local New York time
Can I do using:
TimeZoneInfo.ConvertTime(DateTime.Now, TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time"))
Or I need to consider daylight savings?
Now in my UI I need to display 2 columns. 1) the DateTime from the database and the DateTime in the database converted to GMT
How can I do this?

The TimeZoneInfo class should give you what you need.
var date = (DateTime)reader[0]; // Retrieve data from database however you normally get it
var est = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
var utcTime = TimeZoneInfo.ConvertTimeToUtc(date, est);
var localTime = utcTime.ToLocalTime();
Edit: You modified your question to indicate you have looked at TimeZoneInfo, so this doesn't add much anymore. However to resolve the ambiguous time issue mentioned by Jon, take a look at the IsAmbiguousTime() and GetAmbiguousTimeOffsets() methods to be able to detect values that can't be definitively converted.

Here's a sample to show that it should work as expected. That is, it will do the DST conversion.
DateTime dt1 = new DateTime(2016, 06, 01, 08, 00, 00, DateTimeKind.Unspecified); // Daylight saving time
DateTime dt2 = new DateTime(2016, 12, 01, 08, 00, 00, DateTimeKind.Unspecified); // Standard time
var dt1Converted = TimeZoneInfo.ConvertTimeToUtc(dt1,
TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time"));
var dt2Converted = TimeZoneInfo.ConvertTimeToUtc(dt2,
TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time"));
var diff1 = (dt1Converted - dt1).TotalHours;
var diff2 = (dt2Converted - dt2).TotalHours;
Console.WriteLine($"dt1: {dt1}, converted: {dt1Converted}, diff: {diff1}");
Console.WriteLine($"dt2: {dt2}, converted: {dt2Converted}, diff: {diff2}");
Output:
dt1: 2016-06-01 08:00:00, converted: 2016-06-01 12:00:00, diff: 4
dt2: 2016-12-01 08:00:00, converted: 2016-12-01 13:00:00, diff: 5

Is there any chance you can change this to use DateTimeOffset ? It was designed to resolve all of these problems

Get full day Name from DateTime in C#

I have js calender when I select date from calender it calls C# service which takes string as parameter . It is getting date in format Mon Apr 18 2016 00:00:00 GMT 0500 . I want Monday intead of Mon.
My java Script code is
$scope.deliveryDateTime = { Day: new Date(2015, 11, 28, 14, 57) };
var DeliveryDay = $scope.deliveryDateTimeData.Day;
$http.get(meta.service.GetTimeAvlb+'?day='+ DeliveryDay).
success(function (data) {
debugger;
console.log("Data" + data);
$scope.AvailiableTimeData = data.data;
}
}).
error(function (data) {
});
Here is my C# Service code
public ApiResult GetTimeAvlb( string day )
{
var splitDay = day.Split(' ');
string dayName1 = splitDay[0].ToString();
apiresilt.data = db.TimeAvaliblities.Where(ss => ss.DayName == dayName1).ToList();
return apiresilt;
}
here dayName1 returning Mon while my db has value Monday .

If you really wanna parse this string to DateTime, you have to use your GMT 0500 (Pakistan Standard Time) part as a string literal. DateTime parsing methods does not support timezone names and UTC Offset part without TimeSeparator.
Then you can use DateTime.ToString method with dddd specifier and english-based culture like InvariantCulture.
var s = "Mon Apr 18 2016 00:00:00 GMT 0500 (Pakistan Standard Time)";
var dt = DateTime.ParseExact(s, "ddd MMM dd yyyy HH:mm:ss 'GMT 0500 (Pakistan Standard Time)'",
CultureInfo.InvariantCulture);
Console.WriteLine(dt.ToString("dddd", CultureInfo.InvariantCulture));
By the way, there is no such a thing as date time string. Your data either can be DateTime or string.

.ToString("Format-String") can be used for display date in required format;
DateTime dt = DateTime.Now; will be the current date APR/01/2016
string str = dt.ToString("dddd"); // this will be Friday for 04/01/2016

DateTimeOffset proper usage

If I have a DateTime instance which represents a valid UTC time, and an offset that converts that DateTime to the time zone where it applies, how do I construct a DateTimeOffset instance to represent this?
var utcDateTime = new DateTime(2011, 02, 29, 12, 43, 0, /*DateTimeKind.Utc*/);
var localOffset = TimeSpan.FromHours(2.0);
var dto = ...
// Here the properties should be as follows;
// dto.UtcDateTime = 2011-02-29 12:43:00
// dto.LocalDateTime = 2011-02-29 14:43:00
Perhaps I'm not understanding the DateTimeOffset structure correctly, but I'm unable to get the expected output.
Thanks in advance

Looks like you want:
var utcDateTime = new DateTime(2012, 02, 29, 12, 43, 0, DateTimeKind.Utc);
var dto = new DateTimeOffset(utcDateTime).ToOffset(TimeSpan.FromHours(2));
Note that I changed the year from 2011 (which is not a leap year and does not have 29 days in February) to 2012.
Test:
Console.WriteLine("Utc = {0}, Original = {1}", dto.UtcDateTime, dto.DateTime);
Output:
Utc = 2/29/2012 12:43:00 PM, Original = 2/29/2012 2:43:00 PM
Do note that you probably don't want the LocalDateTime property, which may represent the instant in time as of the local system's timezone.

How to Convert PDT Time string to DateTime

I have the data in string format
"22:48:32 Jul 29, 2011 PDT"
Now I want to convert it into datetime.
How can I do it.

You are probably after this method:
DateTime.Parse(string)
PDT is -7 from GMT, so you can refer to the GMT and subtract 7 hours.
DateTime datetime = DateTime.Parse("Jul 29 2011 22:48:32 GMT"); // notice GMT
datetime = datetime.AddHours(-7); // minus 7 hours