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Why is the conversion from ulong to DateTime returning 0?

I'm trying to convert ULONG to DateTime and as DateTime accepts Ticks as param which are LONG, here's how I do it.
ulong time = 12354;
new DateTime((long)time).ToString("HH:mm:ss");
The result of this is 00:00:00.
I don't understand the result, am I doing something wrong?
P.S. i.Time is not 0, I checked multiple times.

Citing the documentation:
Initializes a new instance of the DateTime structure to a specified number of ticks.
ticks
Type: System.Int64
A date and time expressed in the number of 100-nanosecond intervals that have elapsed since January 1, 0001 at 00:00:00.000 in the Gregorian calendar.
This is 100 nanoseconds which is a super small time unit. So unless your number is larger than 10000000, you don’t even get a single second:
Console.WriteLine(new DateTime((long)10000000).ToString());
// 01.01.0001 00:00:01
So you should really think about what your “time left” (i.Time) value is supposed to mean? Is this really time in the unit of 100 nanoseconds? Very likely not. It’s probably more about seconds or something completely different.
Btw. if the number you have does not actually represent a moment in time, you should not use DateTime. You should use TimeSpan instead. Its long constructor has the same behavior though, but you can use one of the handy static functions to create a time span with the correct unit:
var ts = TimeSpan.FromSeconds(1000);
Console.WriteLine(ts.ToString());
// 00:16:40

Because a tick is 100 nanoseconds, and so 12354 ticks is only 1235400 nanoseconds which is only .0012354 seconds. So your datetime is .0012354 seconds after midnight on 1 Jan in the year one.

timestamp like 6.3527482515083E+17

I'm getting via WSDL from C# application timestamp number like
6.3527482515083E+17
6.3527482515047E+17
6.352748251638E+17
6.3527482514463E+17
All are the times in the past (this year, probably)
I think that's is the datetime counted from YEAR ZERO. I try to count up seconds from ZERO and get someting about 63537810544. But this is not exact, because missing leap years.
exists in PHP any function how to get UNIX timestamp ??? or convert it to STRING datetime ???
I get values via WSDL so I can't reformat it on source...

They are in 100 nanosecond ticks (1/10,000,000 of a second) from 12:00:00 midnight, January 1, 0001. This information can be found in this MSDN article.
A single tick represents one hundred nanoseconds or one ten-millionth of a second. There are 10,000 ticks in a millisecond, or 10 million ticks in a second.
The value of this property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001, which represents DateTime.MinValue. It does not include the number of ticks that are attributable to leap seconds.
The magic constant that represents the number of 100ns ticks between 12:00:00 midnight January 1 0001 and 12:00:00 midnight January 1 1970 (Unix epoch time) is 62135596800000000. So if you subtract that from your numbers you get 100ns ticks since beginning of Unix Epoch time. Divide that by 10,000,000 and you get seconds. And that is usable in PHP. Sample code below to demonstrate (unixepoch is in seconds):
<?php
$msdatetime = 6.3527482515083E+17;
$unixepoch = ($msdatetime - 621355968000000000)/10000000 ;
echo date("Y-m-d H:i:s", $unixepoch);
?>
Output:
2014-02-08 11:55:15
I found this constant listed on this helpful site dealing with the problem of getting unix epoch time from other formats.

Convert Human readable date into an epoch time stamp

I am working on a C# project where I have a date/time in the format of 2012-11-24 15:35:18 and I need to convert this into an epoch time stamp.
Everything I've found on Google is to convert an epoch time stamp into a human readable but I need it to be done the other way round.
Thanks for any help you can provide.

I found this here:
epoch = (DateTime.Now.ToUniversalTime().Ticks - 621355968000000000) / 10000000;
Instead of DateTime.Now, you should be able to input your desired time.

You didn't say your exact use case, but the standard .NET DateTime has a Ticks attribute which is defined as:
The value of this property represents the number of 100-nanosecond
intervals that have elapsed since 12:00:00 midnight, January 1, 0001,
which represents DateTime.MinValue. It does not include the number of
ticks that are attributable to leap seconds.
This is essentially an epoch based time, if it will suit your needs. Otherwise, with this value, you should be easily able to compute a conversion to another epoch time keeping method.

You need to use TryParse:
string input = "2012-11-24 15:35:18";
DateTime dateTime;
if (DateTime.TryParse(input, out dateTime))
{
ulong epoch = (dateTime.ToUniversalTime().Ticks - 621355968000000000) / 10000000;
}

Getting Milliseconds elapsed between arbitrary date and Epoch time

If I write a simple method to return the milliseconds between epoch time and DateTime.UtcNow, I get a proper answer. However, if I write a method to return the milliseconds between some arbitrary date and epoch time, the last three digits are always zero. 'Some arbitrary date' means that I pass in to the method the output of DateTime.Parse("arbitrary date string"). As near as I can make out, the DateTime object returned by .Parse is not returning all the significant digits.
Test method:
static void GetMillis()
{
DateTime dUtc = DateTime.UtcNow;
DateTime epoch = new DateTime(1970,1,1,0,0,0,DateTimeKind.Utc);
double utcmillis = (dUtc - epoch).TotalMilliseconds;
String timestamp = dUtc.ToString();
DateTime arbitrary = (DateTime.Parse(timestamp));
Console.WriteLine("Milliseconds between DateTime.UtcNow {0} \nand epoch time {1} are {2}", dUtc, epoch, utcmillis);
Console.WriteLine("Milliseconds between arbitrary date {0} \nand epoch time {1} are {2}", arbitrary, epoch, (arbitrary - epoch).TotalMilliseconds);
}
Output:
C:\src\vs\epochConverter\epochConverter\bin\Debug
{powem} [54] --> .\epochConverter.exe -debug
Milliseconds between DateTime.UtcNow 8/26/2012 11:12:31 PM
and epoch time 1/1/1970 12:00:00 AM are 1346022751385.8
Milliseconds between arbitrary date 8/26/2012 11:12:31 PM
and epoch time 1/1/1970 12:00:00 AM are 1346022751000
I don't know if I'm doing something grotesquely wrong or not understanding the math here. I've researched in MSDN and can't find anything relating to this difference. I really would like to be able to compute the millis as described -- is it possible?
Thanks.
mp

You want to examine the intermediate values of:
String timestamp = dUtc.ToString();
Just what it returns will depend on your local settings, but it'll be something like 8/26/2012 11:12:31, which is only accurate to the nearest second.
Parsing that of course gives a date-time with 0 milliseconds.
It is therefore correct that your milliseconds-since-epoch method has zeros at that point.
If however you did something like:
arbitrary = new DateTime(2012, 8, 26, 11, 12, 31, 123);
You'd get those 123 milliseconds influencing the result. You can also use a ToString and a ParseExact that includes fractions of a second, or a whole slew of other ways of obtaining a DateTime.
In all, your milliseconds-since-epoch worked perfectly, but your way of getting a date to test it was flawed.

The default DateTime.ToString() format does not include the milliseconds and this is where the data is being lost; it happens before the Parse. To obtain the milliseconds in the string representation, use a custom format:
DateTime.UtcNow.ToString()
// -> 8/26/2012 11:37:24 PM
DateTime.Parse("8/26/2012 11:37:24 PM").Millisecond
// -> 0
DateTime.UtcNow.ToString("yyyy-MM-ddTHH:mm:ss.fffffffK")
// -> 2012-08-26T23:41:17.3085938Z
DateTime.Parse("2012-08-26T23:41:17.3085938Z").Millisecond
// -> 308
See The Round-trip ("O", "o") Format Specifier
to type less. Or, in this case, consider avoiding the conversion entirely :-)
The math is sound.

The math looks reasonable here. Don't forget there are 1000 milliseconds in a 1 second, so any date computation from an arbitrary time that does not include milliseconds vs an almost identical time that includes milliseconds will have an error of +/- 1000 milliseconds.

Convert Date to Milliseconds

I am working with Visual Studio 2010, MVC 3 and C#. I am creating some highcharts and need to have the x-axis be a date. I am pulling the dates from a database and adding them to and array that will then be passed to highcharts. I think highcharts requires the dates to be in millisecond format. Ho do I go about converting a DateTime of '12/20/2011 5:10:13 PM" for example to milliseconds?

Once you figure out what you want to calculate milliseconds from, you can just take one DateTime object from another to get a TimeSpan object. From TimeSpan you can get TotalMilliseconds.
In other words, if start and end are DateTime objects, you can do this:
double milliseconds = (end - start).TotalMilliseconds;

You can use the DateTime.Ticks property and convert the value to milliseconds.
The value of this property represents the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001, which represents DateTime.MinValue. It does not include the number of ticks that are attributable to leap seconds.
A single tick represents one hundred nanoseconds or one ten-millionth of a second. There are 10,000 ticks in a millisecond.

The .Ticks in C# DateTime gives you the value of any time in ticks. You can thereafter convert to milliseconds as shown below:
long dateticks = DateTime.Now.Ticks;
long datemilliseconds = dateticks / TimeSpan.TicksPerMillisecond;

DateTime[] dates = ;
var minDate = dates.Min();
var msDates = dates.Select(date => (date - minDate).TotalMilliseconds).ToArray();