Develop Reference

Parse date time c# with correct timezone and kind

I have a datetime in database which I read using SqlDataReader and then cast it to (DateTime). After the cast its Kind property is DateTimeKind.Unspecified.
Then I have another string which I read from some other source. Its format is like this 2016-01-20T22:20:29.055Z. I do DateTime.Parse("2016-01-20T22:20:29.055Z") and its Kind property is DateTimeKind.Local.
How do I properly parse the both date times for comparison? Do I need to use DateTimeOffsets? How should I parse them?
Thanks

Because SQLReader cannot reasonably infer a DateTimeKind, it leaves it as unspecified. You'll want to use DateTime.SpecifyKind to change the DateTimeKind on your output from the SQLReader to the appropriate value. This works ok if you are only dealing with UTC and one consistent local time zone; otherwise, you really should be using DateTimeOffset in both your code and the SQL Database.
The string "2016-01-20T22:20:29.055Z" is ISO 8601 compliant and is a UTC date; however, DateTime.Parse with only 1 argument can end up performing a conversion to local time. Per the documentation:
Generally, the Parse method returns a DateTime object whose Kind
property is DateTimeKind.Unspecified. However, the Parse method may
also perform time zone conversion and set the value of the Kind
property differently, depending on the values of the s and styles
parameters:
If s contains time zone information, the date and time is converted
to the time in the local time zone and the Kind is DateTimeKind.Local.
If s contains time zone information, and styles includes the
AdjustToUniversalflag, the date and time is converted to Coordinated
Universal Time (UTC) and the Kind is DateTimeKind.Utc.
If s contains the Z or GMT time zone designator, and styles includes
the RoundtripKind flag, the date and time are interpreted as UTC and
the Kind is DateTimeKind.Utc.
Also see UTC gotchas in .NET and SQL Server in Derek Fowler's blog for additional coverage on the topic.

In your second example, 2016-01-20T22:20:29.055Z has timezone information provided with it; the 'Z' at the end indicates that the timestamp is intended for Coordinated Universal Time (UTC). However, DateTime.Parse() will default its conversion using DateTimeKind.Local unless a specific timezone is specified. You can use DateTime.ParseExact to be more specific.
As to why the datetime values in your database are coming out as Unspecified, that's likely because they contain no timezone indication at all. Check to see if your database values specify timezone information, either by using 'Z' at the end or specifying an exact timezone, such as 2016-01-20T22:20:29.055-07:00 (UTC-7).

You can use something like this:
string format = "ddd dd MMM h:mm tt yyyy";
DateTime dateTime = DateTime.ParseExact(dateString, format,
CultureInfo.InvariantCulture);
In format variable, you can put the format you want, and pass it to ParseExact function.
Hope it helps.

You are missing the datetime context (offset) in your database. You should persist it either in a datetimeoffset column or in a datetime column but persisting utc datetimes.
And always better compare two utc datetimes.

I coded a quick C# console app that I pasted in below. This converts a UTC date and time to a string (format similar to the ISO 8601 format described in another post with some extra digits of precision), writes it to a file, reads it from the file (as a string) and then converts it back to a UTC date and time.
It then compares the two UTC Date Time objects, which are both of UTC kind, and they match.
class Program
{
// "2016-01-20T22:20:29.055Z" is ISO 8601 compliant and is a UTC date
const string dtf = "yyyy-MM-ddTHH:mm:ss.fffffffZ";
static void Main(string[] args)
{
string file = #"c:\temp\file.txt";
DateTime dt = DateTime.UtcNow;
using (var sw = new System.IO.StreamWriter(file))
{
sw.WriteLine(dt.ToString(dtf, System.Globalization.CultureInfo.InvariantCulture));
}
DateTime dtin;
using (var sr = new System.IO.StreamReader(file))
{
dtin = DateTime.ParseExact(sr.ReadLine(), dtf, System.Globalization.CultureInfo.InvariantCulture);
}
Console.WriteLine(dt.ToString(dtf) + "\r\n" + dtin.ToString(dtf) + "\r\nEquality:" + (dt == dtin));
Console.ReadLine();
}
}

Is there a way to format a date time object?

So last week, the way our application worked was that the back-end team was storing dates as a string in YYYY-MM-DD formats. This week, they changed it to be a DateTime object instead of a string. So now I'm just creating a DateTime object from the string value on this particular DateTime control we use.
So basically with our custom control , it was like this:
mySearchModelObject.fromDate = myDateRangeControl.Values[0]; //string
mySearchModelObject.toDate = myDateRangeControl.Values[1]; //string
Now it's more like this:
DateTime fromDate, toDate;
DateTime.Tryparse(myDateRangeControl.Values[0], out fromDate);
DateTime.Tryparse(myDateRangeControl.Values[1], out toDate);
mySearchModelObject.fromDate = fromDate;
mySearchModelObject.toDate = toDate;
But searching with the same date range as last week yields different results from the DB.
I'm wondering if it's because our dates were "YYYY-MM-DD" as strings, but now it's getting a date time object in whatever the system's format is + the time itself.
So is there a way to format my DateTime object to still have it in the same YYYY-MM-DD format?

Use DateTime.TryParseExact and provide "yyyy-MM-dd" as format string.
See http://msdn.microsoft.com/en-us/library/h9b85w22

you can do fromDate.ToString("yyyy-MM-dd") to have a date formatted as YYYY-MM-DD
see msdn on standard and custom datetime format
see demo https://dotnetfiddle.net/NZz0HG
also if mySearchModelObject.fromDate is of type object, you can assign a DateTime or a string, no compiler warnings/error.
But when is used, maybe with mySearchModelObject.fromDate.ToString() you get a different result, before was '2014-12-31' and now 12/31/2014 12:00:00 AM

Parse a UTC date string to date in C#

Simple question, I have this string:
string dateString = "7/12/2014 4:42:00 PM";
This is a date string and it's in the UTC timezone.
I need to convert it to a date, so I'm doing the following:
DateTimeOffset dateOffset;
DateTimeOffset.TryParse(dateString, out dateOffset);
DateTime date = dateOffset.UtcDateTime;
The problem:
When I'm parsing the string to date, the code is considering that the dateString is in the Local Timezone of the PC (+3 GMT), and not in the UTC timezone.
So I am getting the following the dateOffset = {7/12/2014 4:42:00 PM +03:00} and thus date = {7/12/2014 1:42:00 PM}
how can I tell him that the date string provided is in the UTC format and not in the local timezone format?
Thanks

how can I tell him that the date string provided is in the UTC format and not in the local timezone format?
Specify a DateTimeStyles value of AssumeUniversal in the call. That tells the parsing code what to do. For example:
// null here means the thread's current culture - adjust it accordingly.
if (DateTimeOffset.TryParse(dateString, null, DateTimeStyles.AssumeUniversal,
out dateOffset))
{
// Valid
}
You should always use the result of TryParse to tell whether or not it's successfully parsed.
If you know the format and the specific culture, I'd personally use DateTimeOffset.TryParseExact. (Well, to be honest I'd use my Noda Time project to start with, but that's a different matter.)

There is another overload of DateTimeOffset.TryParse
DateTimeOffset.TryParse Method (String, IFormatProvider, DateTimeStyles, DateTimeOffset)
which allows you specify DateTimeStyles. One of the DateTimeStyles is AssumeUniversal, which is what you're looking for:
If no time zone is specified in the parsed string, the string is
assumed to denote a UTC. This value cannot be used with AssumeLocal or
RoundtripKind.

Don't know how .Net API provides, but I guess you could probably use ISO8601 format to indicate a UTC timezone before parsing, i.e, first translate 7/12/2014 4:42:00 PM into something 2014-07-02T16:42:00Z, then use try parse using DateTimeOffset

Format Date and Time in .NET

How to format date and time to local system date and time format? I need to format date and time separately. Suppose date is "06/11/2013" and time is "16:00:00" now both need to be formatted to system current date format and time format (with am/pm if 12 hours mode).

DateTime.ToString() takes a string format parameter that allows you to create whatever format you want. http://msdn.microsoft.com/en-us/library/8kb3ddd4.aspx
If you use DateTime.Now to get the current date/time of the server you can then use the .ToString() method to format your output.

using System.Globalization;
string date = DateTime.Now.ToString("MM-dd-yyyy HH:mm:ss tt", CultureInfo.InvariantCulture);

Why is not the day of the week formated in long date format for all languages?

We have used date.ToString ("D") for formatting the date. But when we globalizat the application to other languages ​​we encounter problems. We expect the day of the week to appear when we use the long date format, but it's not lake so for all languages. According http://www.basicdatepicker.com/samples/cultureinfo.aspx, it is far from all language that print out day a week for the long date format. How should we do to format the date?

If you need an explicit format, specify it like so;
DateTime date = DateTime.Now;
string s = date.ToString("dddd, dd MMMM yyyy");
According to the MSDN doco, the "D" format specifier is affected by the Calendar, which is Culture specific.
You shouldn't make assumptions about string formatting or Date display in particular, when internationalising.