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DateTime returns wrong date

I'm trying to get today's date
DateTime todayDateTime = new DateTime();
and I'm getting this:
{1/1/0001 12:00:00 AM}.
Why is this happening?

Use this
DateTime date = DateTime.Now;

Using new DateTime() creates a DateTime with a time of "0".
If you want todays date you need to use DateTime.Today if you want a DateTime object with a date of today and a time of 12:00:00 AM or DateTime.Now if you want a DateTime with the day and time of the moment you called DateTime.Now.

According to MSDN, the constructor for DateTime which takes in a long initializes by using the specified number of ticks since January 1st, 0001, so saying new DateTime(0) yields this time, not the current time.
Instead, use the static field DateTime.Now to get a DateTime representing the current system time.

In your question you are just initializing the Variable todayDateTime but you have never assigned (set it). This is why it is date ("null")/ beginning of our time calculations.
To actually get todays Date, you can use the following:
DateTime today = DateTime.Today;

first of all you need to assigned a value in the datetime.
just use something like this :
DateTime today = DateTime.Today;

TimeSpan to DateTime conversion

I want to convert a Timespan to Datetime. How can I do this?
I found one method on Google:
DateTime dt;
TimeSpan ts="XXX";
//We can covnert 'ts' to 'dt' like this:
dt= Convert.ToDateTime(ts.ToString());
Is there any other way to do this?

It is not very logical to convert TimeSpan to DateTime. Try to understand what leppie said above. TimeSpan is a duration say 6 Days 5 Hours 40 minutes. It is not a Date. If I say 6 Days; Can you deduce a Date from it? The answer is NO unless you have a REFERENCE Date.
So if you want to convert TimeSpan to DateTime you need a reference date. 6 Days & 5 Hours from when? So you can write something like this:
DateTime dt = new DateTime(2012, 01, 01);
TimeSpan ts = new TimeSpan(1, 0, 0, 0, 0);
dt = dt + ts;

While the selected answer is strictly correct, I believe I understand what the OP is trying to get at here as I had a similar issue.
I had a TimeSpan which I wished to display in a grid control (as just hh:mm) but the grid didn't appear to understand TimeSpan, only DateTime . The OP has a similar scenario where only the TimeSpan is the relevant part but didn't consider the necessity of adding the DateTime reference point.
So, as indicated above, I simply added DateTime.MinValue (though any date will do) which is subsequently ignored by the grid when it renders the timespan as a time portion of the resulting date.

TimeSpan can be added to a fresh DateTime to achieve this.
TimeSpan ts="XXX";
DateTime dt = new DateTime() + ts;
But as mentioned before, it is not strictly logical without a valid start date. I have encountered
a use-case where i required only the time aspect. will work fine as long as the logic is correct.

You need a reference date for this to be useful.
An example from
http://msdn.microsoft.com/en-us/library/system.datetime.add.aspx
// Calculate what day of the week is 36 days from this instant.
System.DateTime today = System.DateTime.Now;
System.TimeSpan duration = new System.TimeSpan(36, 0, 0, 0);
System.DateTime answer = today.Add(duration);
System.Console.WriteLine("{0:dddd}", answer);

Worked for me.
var StartTime = new DateTime(item.StartTime.Ticks);

If you only need to show time value in a datagrid or label similar, best way is convert directly time in datetime datatype.
SELECT CONVERT(datetime,myTimeField) as myTimeField FROM Table1

You could also use DateTime.FromFileTime(finishTime) where finishTme is a long containing the ticks of a time. Or FromFileTimeUtc.

An easy method, use ticks:
new DateTime((DateTime.Now - DateTime.Now.AddHours(-1.55)).Ticks).ToString("HH:mm:ss:fff")
This function will give you a date (Without Day / Month / Year)

A problem with all of the above is that the conversion returns the incorrect number of days as specified in the TimeSpan.
Using the above, the below returns 3 and not 2.
Ideas on how to preserve the 2 days in the TimeSpan arguments and return them as the DateTime day?
public void should_return_totaldays()
{
_ts = new TimeSpan(2, 1, 30, 10);
var format = "dd";
var returnedVal = _ts.ToString(format);
Assert.That(returnedVal, Is.EqualTo("2")); //returns 3 not 2
}

First, convert the timespan to a string, then to DateTime, then back to a string:
Convert.ToDateTime(timespan.SelectedTime.ToString()).ToShortTimeString();

Display ticket remaining time

I am programming small page and I want to display expiration time of authentication ticket. I mean not the end, but remaining time. Current code is follows:
DateTime cas = (DateTime)ticket.Expiration.Date;
DateTime cas1 = DateTime.Now;
DateTime cas2 = cas1.Subtract(cas);
However, VS says "Cannot implicitly convert system.timespan into system datetime".
Pls help. Thanks a lot.

Substract method returns a timespan, not a Datetime. Try this :
Timespan cas2 = cas.Subtract(cas1);
[edit] following the comments, the code that should works is simply :
TimeSpan remaining = ticket.Expiration.Substract(DateTime.Now);
You don't have to case Expiration, as it's a DateTime property.

You can use operator overloading. The type returned by subtracting one DateTime from another is a TimeSpan:
TimeSpan remainingTime = ticket.Expiration - DateTime.Now;

How to get the time difference between two DateTime objects?

emp = moduleEmployee.ReturnEmployeeDAO().FetchEmployeeByID(emp);
DateTime shiftStartTime = emp.Shift.StartTime;
DateTime shiftEndTime = emp.Shift.EndTime;
DateTime attTime = att.Time;
According to the above code my shiftStartTime is 11.00 PM and shiftEndTime is 7.00 AM. and attTime or signIntime is 1.00 AM. then how to calculate the difference between shiftStartTime and attTime. where the difference should be 2 hour.
please help.....
Thanks Rusho

If you subtract two DateTime objects, you get a TimeSpan.
A TimeSpan then has properties for TotalMilliseconds, TotalSeconds, etc.
You want the TimeSpan.TotalHours
int shiftHours = (attTime - shiftStartTime).TotalHours;

Just subtract one time from the other and you'll get a TimeSpan object.
see http://msdn.microsoft.com/en-us/library/1905yhe2.aspx

TimeSpan diff = att.Time.Subtract(emp.Shift.StartTime);

are you asking for something like this: ?
var timeSpan = (attTime - shiftStartTime);
the result is a TimeSpan where you can check how many hours, minutes, days, seconds and so on...

get the integer between the dates

i am programming in c# and i have question:
how can i get the integer value between a date.
for example : 12/6/2010 and 12/18/2010
how can i get at 1st i=6 and in the second i=18

DateTime dt = DateTime.Parse("12/6/2010");
int i = dt.Day;
See: DateTime reference

It's not clear what you are asking, but you can access the day from a DateTime as follows:
DateTime dt=DateTime.Now;
int day=dt.Day;
If you want a time difference in days:
DateTime dt1=new DateTime(2010,12,6);
DateTime dt2=new DateTime(2010,12,18);
int dayDelta=(dt2-dt1).Days;

If you have a DateTime variable (birth, by example). you can use birth.Month to obtain the month, birth.Day to obtain the day, etc.

You can use "Days" method of DateTime class.