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C# TimeOnly value to localtime

I am trying to change TimeOnly value to local TimeOnly.
What is the best way to do this in .NET? There isn't built in method to do this.
Thank you.

Because of daylight savings, local time has no meaning unless you also know the date. You need a date as part of the value or you can't really know what time to use for a given local timezone.

IANA/Olson timezone support in C#

C# supports different timezone id's across the globe. Please find list of time zones that are being supported by C# in below link:
https://msdn.microsoft.com/en-us/library/gg154758.aspx
The timezone id's are used in C# library functions to convert times across the timezones.
[e.g. TimeZoneInfo.ConvertTimeBySystemTimeZoneId("Hawaiian Standard Time")]
Similarly I want support for AMERICA/MIQUELON, which is not present in the msdn list provided in above link.
Can somebody please provide workaround for this specific timezone?

Time zone identifiers like "America/Miquelon" and the others you listed (before editing your question) are from the IANA time zone database. You can read more in the timezone tag wiki and on Wikipedia.
Note that they are usually presented in mixed case form, rather than in all capital letters.
The easiest and best way to work with these in .NET is via the Noda Time library.
For example:
DateTimeZone tz = DateTimeZoneProviders.Tzdb["America/Miquelon"];
Instant now = SystemClock.Instance.Now;
ZonedDateTime converted = now.InZone(tz);

Local to GMT DateTime Conversion

I'm working with the Amazon API. I need to convert local time (EDT) to a DateTime that complies with the following documentation from Amazon:
You can specify the FulfillmentDate with or without time zone information:
2006-12-11T09:50:00 - local time zome applies
2006-12-11T09:50:00+02:00 - GMT time zone applies
For locales affected by Daylight Saving Time, adjust the information, if necessary.
Daylight Saving Time is not automatically taken into consideration.
I thought I needed to do something like shown in this SO thread, but apparently wrong, because when I upload the date using that method, Amazon shows it as a day before. I can confirm this by using this online converter tool.
For example:
My local time is "7/25/2012 00:00:00" (EDT).
Using above SO method, and formatted, it's now
"2012-07-25T01:00:00-04:00".
But it converts to the 24th, specifically "Tuesday, July 24, 2012 at
21:00:00".
Obviously I'm doing something wrong here - I'd appreciate if someone can enlighten me.
Thank you!

I would recommend using:
String xmlDateString = XmlConvert.ToString(DateTime.UtcNow,XmlDateTimeSerializationMode.Local);

Obviously Amazon converts your local time information back to UTC time (which is based on your input 4 hours back in time: Tuesday, July 24, 2012 at 21:00:00 and therefore correct).
Which result have you been expected?

I think I can introduce a "joda time" project written by Jon Skeet. You can refer to link pros and cons of joda time

How to find Current Time of different culture i.e different timezone in c# asp.net?

Like DateTime.Now gives us current date and time with respect to current system.
How can we find Current Time of different culture i.e different timezone using c# asp.net???
I find SystemTimeToTzSpecificLocalTime Function but how can i used this one???

If you're using .NET 3.5 or later, you can use TimeZoneInfo:
TimeZoneInfo otherZone = ...;
DateTime otherZoneTimeNow = TimeZoneInfo.ConvertTime(DateTime.UtcNow, otherZone);
You need to be somewhat careful using TimeZoneInfo - different DateTime "kinds" do different things - you should read the docs for any call you make carefully. (I recently blogged about the problems with DateTime... TimeZoneInfo basically has to handle the ambiguity.)

You can use a service, like the Yahoo! Web Services API, to pull this information and more. You can get time zone, local time, population, etc. with the Yahoo! Web Services API. The biggest drawback to that approach is the maximum daily hit count.
You can check out this link for more details:
http://developer.yahoo.com/flash/maps/classreference/com/yahoo/maps/webservices/geocoder/GeocoderResult.html

Get timezone from DateTime

Does the .Net DateTime contain information about time zone where it was created?
I have a library parsing DateTime from a format that has "+zz" at the end, and while it parses correctly and adjusts a local time, I need to get what the specific time zone was from the DateTime object.
Is this possible at all? All I can see is DateTime.Kind, which specifies if time is local or UTC.

DateTime itself contains no real timezone information. It may know if it's UTC or local, but not what local really means.
DateTimeOffset is somewhat better - that's basically a UTC time and an offset. However, that's still not really enough to determine the timezone, as many different timezones can have the same offset at any one point in time. This sounds like it may be good enough for you though, as all you've got to work with when parsing the date/time is the offset.
The support for time zones as of .NET 3.5 is a lot better than it was, but I'd really like to see a standard "ZonedDateTime" or something like that - a UTC time and an actual time zone. It's easy to build your own, but it would be nice to see it in the standard libraries.
EDIT: Nearly four years later, I'd now suggest using Noda Time which has a rather richer set of date/time types. I'm biased though, as the main author of Noda Time :)

No.
A developer is responsible for keeping track of time-zone information associated with a DateTime value via some external mechanism.
A quote from an excellent article here.
A must read for every .Net developer.
So my advice is to write a little wrapper class that suits your needs.

There is a public domain TimeZone library for .NET. Really useful. It will answer your needs.
Solving the general-case timezone problem is harder than you think.

You could use TimeZoneInfo class
The TimeZone class recognizes local time zone, and can convert times between Coordinated Universal Time (UTC) and local time. A TimeZoneInfo object can represent any time zone, and methods of the TimeZoneInfo class can be used to convert the time in one time zone to the corresponding time in any other time zone. The members of the TimeZoneInfo class support the following operations:
Retrieving a time zone that is already defined by the operating
system.
Enumerating the time zones that are available on a system.
Converting times between different time zones.
Creating a new time zone that is not already defined by the
operating system.
Serializing a time zone for later retrieval.

From the API (http://msdn.microsoft.com/en-us/library/system.datetime_members(VS.71).aspx) it does not seem it can show the name of the time zone used.

DateTime does not know its timezone offset. There is no built-in method to return the offset or the timezone name (e.g. EAT, CEST, EST etc).
Like suggested by others, you can convert your date to UTC:
DateTime localtime = new DateTime.Now;
var utctime = localtime.ToUniversalTime();
and then only calculate the difference:
TimeSpan difference = localtime - utctime;
Also you may convert one time to another by using the DateTimeOffset:
DateTimeOffset targetTime = DateTimeOffset.Now.ToOffset(new TimeSpan(5, 30, 0));
But this is sort of lossy compression - the offset alone cannot tell you which time zone it is as two different countries may be in different time zones and have the same time only for part of the year (eg. South Africa and Europe). Also, be aware that summer daylight saving time may be introduced at different dates (EST vs CET - a 3-week difference).
You can get the name of your local system time zone using TimeZoneInfo class:
TimeZoneInfo localZone = TimeZoneInfo.Local;
localZone.IsDaylightSavingTime(localtime) ? localZone.DaylightName : localZone.StandardName
I agree with Gerrie Schenck, please read the article he suggested.

Generally the practice would be to pass data as a DateTime with a "timezone" of UTC and then pass a TimeZoneInfo object and when you are ready to display the data, you use the TimeZoneInfo object to convert the UTC DateTime.
The other option is to set the DateTime with the current timezone, and then make sure the "timezone" is unknown for the DateTime object, then make sure the DateTime is again passed with a TimeZoneInfo that indicates the TimeZone of the DateTime passed.
As others have indicated here, it would be nice if Microsoft got on top of this and created one nice object to do it all, but for now you have to deal with two objects.