Sharepoint Datetime picker does not return correct date

What do you mean by edit that field? Do you mean when someone selects a value or do you mean when you edit a value in code?

When someone selects the value using datetime picker -> ItemUpdating() called
within ItemUpdating() I compare AfterProperties(Changed Value) and properties.ListItem (Original Value). I then take difference of both dates to determine how many days a task moved in past or future. But when I look at the AfterProperties(Chnaged value) its not the one selected by user and so i get error in number of days calculation.

I hope i am clear now. Thank you!

Hello,
As I can see the issue is related to Regional Settings of the SharePoint Site/Server.You need to check if your server that run your code is in the same Time Zone with your SharePoint Site. If it's not the same you will need to set your Time Zone settings in the code before the field update.
Please take a look at this article for TimeZoneInfo class information:
http://msdn.microsoft.com/en-us/library/system.timezoneinfo.aspx

You can use ConvertTime Method to convert the local system date to the correct date according to SharePoint Time Zone.

I hope it helps.

Thanks svetaye! But if i see Site Actions -> Site Settings -> Site Admin -> Regional settings -> Timezone its same as my server (where code runs)!

Are you using a calculated column to store this value or a numeric or string column with a default value calculation?

I am using Date and Time type with default value selected none and format is Date and Time.

Yes, but what type of column are you doing your difference calculation in? Does the value for the difference column stay the same as if it's not being dynamically calculated?

OK I am posting the code here...
OnJobStartDate() function is called in

void ItemUpdating(SPItemEventProperties properties)

Select allOpen in new window

private void OnJobStartDateChanging(SPItemEventProperties properties)
        {
            
            DateTime changedJobStartDate = DateTime.Parse(properties.AfterProperties[properties.ListItem.Fields[COL_JOB_START_DATE].InternalName].ToString());
            DateTime originalJobStartDate = ((DateTime)properties.ListItem[COL_JOB_START_DATE]);

            if (!changedJobStartDate.Equals(originalJobStartDate))
            {
                SPWeb site = properties.OpenWeb();
                SPList jobList = site.Lists[LIST_JOBS];
                SPQuery q = new SPQuery();

                TimeSpan timeSpan = changedJobStartDate.Subtract(originalJobStartDate);
                string msg = "Original Date : " + originalJobStartDate.ToString() +
                         ",Changed Date : " + changedJobStartDate.ToString() +
                         ",Timespan : " + timeSpan.ToString();

                WriteToEventViewer(msg, EventLogEntryType.Information, 200);
                SPFolder jobFolder = jobList.RootFolder.SubFolders[properties.ListItem.Title];
                q.Folder = jobFolder;

                SPListItemCollection tasks = jobList.GetItems(q);
                foreach (SPListItem i in tasks)
                {
                    DateTime taskStartDate = ((DateTime)i[COL_TASK_START_DATE]);
                    i[COL_TASK_START_DATE] = taskStartDate.Add(timeSpan);
                    i.Update();
                }

            }
        }

Select allOpen in new window

I Job Start Date it using UI
Job Start Date [Before] : 2/16/2013 12:00 AM
Job Start Date [After] : 2/18/2013 12:00 AM

In event log I am getting following
Original Date : 2/16/2013 12:00:00 AM,Changed Date : 2/17/2013 7:00:00 PM,Timespan : 1.19:00:00

So I am getting wrong timespan and so calculation is not correct!

OK, so the event log is where the calculated value is stored rather than a column within the list. I don't know whether you already walked through the debugger, but it could be possible this line is causing you the problem?

SPList jobList = site.Lists[LIST_JOBS];

I think you need quotes around LIST_JOBS unless it is used as some sort of global string variable.

SPList jobList = site.Lists["LIST_JOBS"];

I don't understand why the code even works at all and why VS isn't flagging this, so I might be missing something, but I've never seen it written the way you did..

yes LIST_JOBS is

 private const string LIST_JOBS = "Jobs"; 

Select allOpen in new window

Other then this why do you believe it's a non-standard code? I mean I am trying to just update date fields in child items by difference of dates in parent item(Folder). Yes, I am new to sharepoint customization but the kind of thing I am doing looks very normal.

I assume COL_JOB_START_DATE and COL_JOB_START_DATE are global as well.

Seems like this is what's failing
DateTime changedJobStartDate = DateTime.Parse(properties.AfterProperties[properties.ListItem.Fields[COL_JOB_START_DATE].InternalName].ToString());

What value do you see when you walk through the debugger? You should see a value for that right at the beginning of execution.

OK, I dont have VS Pro (Using VS Express). And it looks like VS Express cannot attach debugger to a w2wp.exe. However I added line suggested by you and got follwing

Original Date : 2/16/2013 12:00:00 AM,Changed Date : 2/17/2013 7:00:00 PM,Timespan : 1.19:00:00,From Server : 2/22/2013 8:34:21 AM

While actual time is 2/22/2013 1:22:00 PM (in System Date and Time dialog box)..how is that possible!

I don't know the why at the moment and somebody else might. But I think we're getting somewhere and maybe we don't need to look at your code because this oddity certainly would need to be understood first to gain a stable basis for general debugging of the problem. As far as I can see, your code looks really solid. It's just a shame you can't walk through it in the debugger to make sure.