In windowsphone converting current time into millisecond - windows-phone-7

Question

i have a time format like this:
string s = DateTime.Now.ToString();
which gives me output like
11/29/2013 6:26:13PM
Now how can i convert this output into millisecond in windowsPhone???
Updated:
First i want to save the current time when the user launch my app. after that whenever the user launch my app again then i also get the time and compare the current launching time with previously stored time and check whether the time difference becomes "one day" or not.
For this comparison i need to covert 11/29/2013 6:26:13PM this into millisecond.
Another question tell me how can i convert "6:26:13PM" only this into millisecond??

Answer 1

If I understood correctly just do this:
Create a date from your input:
DateTime yourInitialDateTime = DateTime.Parse("11/29/2013 6:26:13PM");
After that
TimeSpan span = DateTime.Now - yourInitialDateTime;
So in span.TotalDays you will have how many days has passed.
Edit
If you have only the time of day and want to know the millisecond of that time you must add a date and subtract it with hour 0:00:00 like this:
string dummyDate = "01/01/0001";
DateTime end = DateTime.Parse(dummyDate + " " + "6:26:13PM");
var milli = end.Subtract(new DateTime()).TotalMilliseconds;
That is it.

Answer 2

Try this.
var ThatDay = DateTime.Now.AddDays(-1); //This is hard coded but you have to get from where you are storing.
var Today = DateTime.Now;
var Diff = (Today - ThatDay).Milliseconds;
var FriendlyDiff = (Today - ThatDay).ToFriendlyDisplay(5);
public static class TimeSpanExtensions
{
private enum TimeSpanElement
{
Millisecond,
Second,
Minute,
Hour,
Day
}
public static string ToFriendlyDisplay(this TimeSpan timeSpan, int maxNrOfElements)
{
maxNrOfElements = Math.Max(Math.Min(maxNrOfElements, 5), 1);
var parts = new[]
{
Tuple.Create(TimeSpanElement.Day, timeSpan.Days),
Tuple.Create(TimeSpanElement.Hour, timeSpan.Hours),
Tuple.Create(TimeSpanElement.Minute, timeSpan.Minutes),
Tuple.Create(TimeSpanElement.Second, timeSpan.Seconds),
Tuple.Create(TimeSpanElement.Millisecond, timeSpan.Milliseconds)
}
.SkipWhile(i => i.Item2 <= 0)
.Take(maxNrOfElements);
return string.Join(", ", parts.Select(p => string.Format("{0} {1}{2}", p.Item2, p.Item1, p.Item2 > 1 ? "s" : string.Empty)));
}
}