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TimeZoneInfo.ConvertTimeFromUTC produce different output then TimeZone.BaseUTCOffset

I have a UTC date-time, I need to convert it to EST time zone. It should be as simple as this
var easternZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
var dt = DateTime.SpecifyKind(value, DateTimeKind.Utc);
return TimeZoneInfo.ConvertTimeFromUtc(dt, easternZone);
So my input date is
02-08-2019 22:53:32
and the result value is
02-08-2019 18:53:32
It deduct 4 hours from given time.
But if I check the Offset between Eastern Standard Time Zone and UTC time zone then the value it return is
easternZone.BaseUtcOffset {-05:00:00} System.TimeSpan
If this is true then above result value should be
02-08-2019 17:53:32
I am not sure what I am missing here.

I am not sure what I am missing here.
BaseUtcOffset does not take into account daylight saving time (it can't, since it doesn't know what specific date you are interested in). You likely want to use GetUtcOffset:
The returned time span includes any differences due to the application
of adjustment rules to the current time zone. It differs from the
BaseUtcOffset property, which returns the difference between
Coordinated Universal Time (UTC) and the time zone's standard time
and, therefore, does not take adjustment rules into account.
Adjustment Rule is discussed here (emphasis mine):
Provides information about a time zone adjustment, such as the
transition to and from daylight saving time.
As a general rule, if dates are ever <= 1 hour out from what you expect, look into daylight savings issues.
To illustrate the impact of daylight saving time:
var timeUtc = Convert.ToDateTime("01-01-2019 22:53:32");
var easternZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
var dt = DateTime.SpecifyKind(timeUtc, DateTimeKind.Utc);
Console.WriteLine(TimeZoneInfo.ConvertTimeFromUtc(dt, easternZone));
Console.WriteLine(easternZone.GetUtcOffset(dt));
timeUtc = Convert.ToDateTime("07-07-2019 22:53:32");
easternZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
dt = DateTime.SpecifyKind(timeUtc, DateTimeKind.Utc);
Console.WriteLine(TimeZoneInfo.ConvertTimeFromUtc(dt, easternZone));
Console.WriteLine(easternZone.GetUtcOffset(dt));
The above code will output:
1/1/2019 5:53:32 PM
-05:00:00
7/7/2019 6:53:32 PM
-04:00:00

Try This :
var timeUtc = Convert.ToDateTime("02-08-2019 22:53:32");
TimeZoneInfo easternZone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
DateTime easternTime = TimeZoneInfo.ConvertTimeFromUtc(timeUtc, easternZone);
Console.WriteLine(easternTime);

Get time zone with UTC conversion

I have the system date in BST . I want to convert it to UTC. So did the below:
string utcDate= TimeZoneInfo.ConvertTimeToUtc(dt).ToString("dd/MM/yyyy HH:mm:ss");
What I want is to get the zone along with the Date in UTC. Pls consider the daylight savings.
Example: 2019-07-08T23:59:00+01:00.

A few things:
The string format you gave the example of, 2019-07-08T23:59:00+01:00 is part of the ISO 8601 specification. To be precise, it is the "complete date and time of day representation" of the "ISO 8601 Extended Format". It also the format defined by RFC 3339.
In this format, the date and time portion represent the local time, as denoted by the time zone offset portion. In other words, the values are not in UTC, but already adjusted. In your example, 2019-07-08T23:59:00 is the local time and UTC+01:00 is in effect at that time. The corresponding UTC time would thus be an hour earlier, 2019-07-08T22:59:00Z.
You seem to be asking for the date in UTC but with an offset that includes daylight saving time. That is impossible, as UTC does not observe daylight saving time. The offset from UTC is always zero. You can read more about UTC here.
The offset of UTC itself is denoted with Z, but can also be represented with +00:00, which can be thought of as "zero offset from UTC". In other words, if you are referring to UTC time use the Z, and if you are referring to a local time that is aligned to UTC (such as GMT in London in the winter, or Iceland, etc.) use +00:00.
In your question, you say you want the system time in UTC with the offset. I will assume by "system time" you mean the current time of the clock on the system. That is provided by DateTime.UtcNow or DateTimeOffset.UtcNow. These return either a DateTime or DateTimeOffset structure - not a string. Since you wanted a string in a specific format, then you should first ask for the current time, and then format it as a string with ToString:
using System.Globalization;
...
string a = DateTime.UtcNow.ToString("yyyy-MM-dd'T'HH:mm:ssK", CultureInfo.InvariantCulture);
// output example: "2019-07-08T22:59:00Z"
string b = DateTimeOffset.UtcNow.ToString("yyyy-MM-dd'T'HH:mm:sszzz", CultureInfo.InvariantCulture);
// output example: "2019-07-08T22:59:00+00:00"
If what you actually wanted was the local time, such that the offset would be +00:00 in the winter and +01:00 in the summer (in the UK), then use Now instead of UtcNow. This gives the local time in the time zone of the computer where the code is running.
string c = DateTime.Now.ToString("yyyy-MM-dd'T'HH:mm:ssK", CultureInfo.InvariantCulture);
// output example: "2019-07-08T23:59:00+01:00"
string d = DateTimeOffset.Now.ToString("yyyy-MM-dd'T'HH:mm:sszzz", CultureInfo.InvariantCulture);
// output example: "2019-07-08T23:59:00+01:00"
If you actually wanted the time in the UK regardless of what the time zone of the local computer was on, then you'd have to first get the UTC time and then convert it to UK time before creating the string.
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("GMT Standard Time");
string e = TimeZoneInfo.ConvertTime(DateTime.UtcNow, tzi).ToString("yyyy-MM-dd'T'HH:mm:ssK", CultureInfo.InvariantCulture);
// output example: "2019-07-08T23:59:00"
string f = TimeZoneInfo.ConvertTime(DateTimeOffset.UtcNow, tzi).ToString("yyyy-MM-dd'T'HH:mm:sszzz", CultureInfo.InvariantCulture);
// output example: "2019-07-08T23:59:00+01:00"
In example e, note that a DateTime can't store an arbitrary offset as the result of time zone conversion, and thus you get DateTimeKind.Unspecified assigned to the Kind property, which results in no offset being in the string representation. Thus most of the time you should use a DateTimeOffset (example f) instead.
Also, note the time zone ID of "GMT Standard Time" is the correct ID to use for the UK on Windows platforms. It correctly switches between GMT and BST when appropriate. If you are running .NET Core on non-Windows platforms (Linux, OSX, etc.), then you should use "Europe/London" instead. Or if you are wanting to write code that is platform-neutral then you can use my TimeZoneConverter library, which allows you to provide either form and run on any platform.
In your code example, you didn't call any of the "now" functions, but gave a dt variable. Assuming this is a DateTime, the result of calling TimeZoneInfo.ConvertTimeToUtc will depend on the Kind property of that variable. If it's DateTimeKind.Utc, then no conversion is performed. If it's DateTimeKind.Local or DateTimeKind.Unspecified, then the value is converted from the computer's local time zone to UTC.
Lastly, keep in mind that when talking to an international audience, time zone abbreviations can be ambiguous. I could deduce by "BST" that you meant British Summer Time, but only because you showed a +01:00 offset in your question. "BST" can also stand for "Bangladesh Standard Time" (+06:00), or "Bougainville Standard Time" (+11:00).

I guess you can do something like this:
var dt = DateTime.Now;
string utcDate = dt.ToUniversalTime().ToString("dd/MM/yyyy HH:mm:ss") +
dt.ToString(" zzz");
Output: (I'm in EET)
14/07/2019 20:02:17 +02:00
But be aware that this could be confusing to people. The standard way is that the timezone follows the local date, not the universal date.

How to get the offset when converting time to specific timezone and then UTC? C#

I am trying to convert date to UTC format where I can get correct offset. I am using ToString("O") in simple DateTime.Now which works.
Now when I am converting my current time (EST) to CST (Central) or MST (Mountain) then I am not getting offset. What am I missing here? Is there any other way to do it?
Code:
var currentTimeToUtc = DateTime.Now.ToString("O");
// Output = "2018-12-27T12:31:21.9946661-05:00" --This is perfect.
var centralTime = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(DateTime.Now, "Central Standard Time");
var centralTimeToUtc = centralTime.ToString("O");
// Output = "2018-12-27T11:31:19.8046052"
// Expected Output = "2018-12-27T11:31:19.8046052-06:00"
var mountainTime = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(DateTime.Now, "Mountain Standard Time");
var mountainTimeToUtc = mountainTime.ToString("O");
// Output = "2018-12-27T10:31:25.2438418"
// Expected Output = "2018-12-27T10:31:25.2438418-07:00"

This is the expected behavior of DateTime. If you need to keep time zone information, use DateTimeOffset instead.
The reason for the difference in the output is that DateTime.Now and centralTime / mountainTime are of different kind: DateTime before conversion is Local, but after conversion it becomes Unspecified.
Run the program below to confirm this:
var now = DateTime.Now;
Console.WriteLine(now.Kind);
var centralTime = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(now, "Central Standard Time");
Console.WriteLine(centralTime.Kind);
var mountainTime = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(now, "Mountain Standard Time");
Console.WriteLine(mountainTime.Kind);
The behavior cannot be changed because DateTime does not store offset; it relies on two well-known offsets for interpretation of the time zone - Local means your local time zone, and UTC means UTC time zone.
The third option, Unspecified, means that the value of DateTime cannot be interpreted as an absolute value by itself, because time zone has been stripped from it. Your code knows what time zone it is, because you did the conversion, but the information about the time zone is part of your program's design, not part of the corresponding DateTime object. .NET added DateTimeOffset objects specifically to address this problem.

How to use Standard Time Only in TimezoneInfo.ConvertTime C#

I am having a Issue with the C# function of TimeZoneInfo.ConvertTime().
What i need to get is the Standard Time not the DST but i'm only getting DST is there a way to Tell the Function to only get the Result in Standard Time.
My local Timezone is UTC -6:00 Central America Standard Time, so if my time is 12:00 PM the Conversion i'm getting is throwing it at 2 PM Eastern Time but i need it to tell me it's 1:00 PM.
public static DateTime TimetoEst( DateTime timenow)
{
var currentTimeZone = TimeZone.CurrentTimeZone.GetUtcOffset(timenow).ToString();
var estzone = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
var conver = TimeZoneInfo.ConvertTime(timenow, estzone);
return conver;
}
Thanks

A couple of things:
The ID "Eastern Standard Time" represents both EST and EDT, with the appropriate transitions in place. It would more appropriately be called "Eastern Time", but alas this is the identifier and the convention used by Windows time zones.
The Eastern Time zone really does transition in and out of daylight saving time. If you were to always adjust to just Eastern Standard Time (UTC-5), you would be ignoring the reality of timekeeping in that region - that it is in Eastern Daylight Time (UTC-4) for dates in the summer months.
Your code will indeed return EST, but only for date values that are outside of the DST period.
Now, if you still think this is what you want to do - then you can do it without the TimeZoneInfo object at all. Simply adjust the result from the offset that applies to your source value, to the UTC-5 offset that applies to EST.
public static DateTime TimetoEst(DateTime timenow)
{
var dto = new DateTimeOffset(timenow); // will use .Kind to decide the offset
var converted = dto.ToOffset(TimeSpan.FromHours(-5));
return converted.DateTime;
}
This is what you asked, but for the record - I don't think this is the best plan. Besides the issues above - assuming that the input value should be interpreted based on the local time zone is not necessarily a good idea - and unless the input time has a .Kind of DateTimeKind.Utc, it will indeed use the computer's local time zone.
You did label the variable as timenow. If you are just after a DateTime which represents the current time in a fixed offset, then it's much safer just to get it like so:
DateTime dt = DateTimeOffset.UtcNow.ToOffset(TimeSpan.FromHours(-5)).DateTime;
And if you really want the current time in the Eastern Time zone, taking DST into account when appropriate, then:
DateTime dt = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(DateTime.UtcNow,
"Eastern Standard Time");

How to tell if it's British Summer Time

I have the following code, which should return an offset of 60 (to show that in the UK at present, we are in British Summer Time - ie. 60 minutes ahead of GMT):
var info = TimeZoneInfo.FindSystemTimeZoneById("Greenwich Standard Time");
DateTimeOffset localServerTime = DateTimeOffset.Now;
double off = localServerTime.Offset.TotalMinutes;
return off;
However, it returns 0.
Could anyone please help fix this for me?

Use TimeZoneInfo.IsDaylightSavingTime Method (DateTimeOffset) to find if it is currently Daylight saving for your Timezone.
var info = TimeZoneInfo.FindSystemTimeZoneById("Greenwich Standard Time");
DateTimeOffset localServerTime = DateTimeOffset.Now;
bool isDaylightSaving = info.IsDaylightSavingTime(localServerTime);
There are further examples here

Your machine is not configured correctly if you get 0 and live in the UK. Probable causes are:
The machine's time zone is not set correctly. Click the clock on the taskbar to correct.
The machine is not configured to observe daylight savings. Click the clock.
The database that TimeZoneInfo consults for daylight savings rules in out of date or corrupted. It is stored in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones registry key.
Be careful about making radical changes, having it configured wrong might well have been done intentionally to work around some kind of flaw in a business-critical app that runs on the server. Talk to whomever administers the server first.

Another option is to use Noda Time.
The following code works with Noda Time 1.4 and higher:
var zone = NodaTime.TimeZones.TzdbDateTimeZoneSource.Default.ForId("Europe/London");
var zonedClock = NodaTime.SystemClock.Instance.InZone(zone);
var zonedDateTime = zonedClock.GetCurrentZonedDateTime();
bool isDST = zonedDateTime.IsDaylightSavingTime();
Console.WriteLine(isDST);
zone is a DateTimeZone object representing the UK's timezone, "Europe/London"
zonedClock is a ZonedClock object which represents, in this case, the system clock and the UK's timezone
zonedDateTime is a ZonedDateTime object representing the current date and time in the timezone ("the current instant provided by the underlying clock, adjusted to the time zone of this object")
isDST is a boolean indicating whether the current instant is in DST or not. At the time of writing (April 2018) this evaluates to true
With earlier versions of Noda where ZonedClock is not available, we can do this instead:
var zone = NodaTime.TimeZones.TzdbDateTimeZoneSource.Default.ForId("Europe/London");
var now = Instant.FromDateTimeOffset(DateTimeOffset.Now);
var zonedDateTime = new ZonedDateTime(now, zone);
bool isDST = zonedDateTime.IsDaylightSavingTime();

To master conversion from one timezone to anther you need to see what's supported (how?) and what's not.
foreach (var tz in TimeZoneInfo.GetSystemTimeZones())
{
Console.WriteLine("TimeZone Offset: {0} Name : {1}, Supports DLS: {2}", tz.BaseUtcOffset,tz.StandardName,tz.SupportsDaylightSavingTime);
}
This should give you the list all timezones including info about DayLightSaving.
Notice that:
TimeZone Offset: 00:00:00 Name : Greenwich Standard Time, Supports DLS: False
TimeZone Offset: 00:00:00 Name : GMT Standard Time, Supports DLS: True
So you need to use "GMT Standard Time" because it supports daylight saving already. No work needs to be done.
Here is sample code:
private static string GetBSTTimeStamp(string timestamp)
{
DateTime dt = DateTime.Parse(timestamp);
//TimeZoneInfo bst = TimeZoneInfo.FindSystemTimeZoneById("GMT Standard Time");
//Console.WriteLine("Time zone supports dls? {0}", bst.SupportsDaylightSavingTime);
//Console.WriteLine("Time zone offset? {0}", bst.BaseUtcOffset);
DateTime dateTimeInUtc = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(dt, "Eastern Standard Time", "GMT Standard Time");
return dateTimeInUtc.ToString();
}