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C# Converting string to DateTime without using DateTimeOffset

I'm trying to bring over facebook events to my website. They will be coming from different regions. For example, an event is in Eastern Time (-4 hours difference from UTC) and my local time is Central time (-5 hours difference from UTC).
I am calling their graph API from a console app. I get the date of the events like this:
// get event items
me = fbClient.Get(url);
var startTime = me["start_time"];
var endTime = me["end_time"];
the start time shows: "2017-04-30T13:00:00-0400" object {string}
When I try to convert that string into a DateColumn type, it changes the output time to:
var dateTime = Convert.ToDateTime(startTime);
{4/30/2017 12:00:00 PM}
It shifted the hour from 13 -> 12, how do I convert the string into date using DateTime and not using DateTimeoffset?
This examples shows how to do it using DateTimeOffset, but I need mine in DateTime type?
https://stackoverflow.com/a/19403747/1019042

You can use the DateTime property of DateTimeOffset like the answer accepted in the link you've provided.
Or, if you really like to do it just with DateTime you can if you cut the timezone from the string:
var dt = DateTime.ParseExact(startTime.Substring(0,19),
"yyyy-MM-ddTHH:mm:ss",
CultureInfo.InvariantCulture);

What are valid UTCDateTime type string formats for AIF transfomrmations?

Im am trying to write a .net class that transforms a piece of xml to a AX UtcDateTime type.
The class is used in an inbound transformation.
Original xml:
<DateTime>
<Date>2014-06-12</Date>
<Time>10:52:00</Time>
<Zone>+02:00</Zone>
</DateTime>
My resulting xml leads to an exeption in the exeptionlog:
"The value '2014-06-12T12:52:00+02:00' is not a valid UtcDateTime type."
I think AIF expect the Z at the end of the value, and I am not sure if the localDateTime is mandatory and or if the milliseconds are a requirement.
I would like to know how the UtcDateTime field in transformed xml should be formatted to be accepted by AIF.
Like so:
<MessageHeaderDateTime localDateTime="2014-06-12T10:52:00+02:00">2014-06-12T08:52:00Z</MessageHeaderDateTime>
or like so:
<MessageHeaderDateTime localDateTime="2014-06-12T10:52:00.1108723+02:00">2014-06-12T08:52:00.1108723Z</MessageHeaderDateTime>
or are other things missing?
My Code
DateTime netdttm = new DateTime(year, month, day, hour, minute, second, DateTimeKind.Utc);
TimeSpan timespan = new TimeSpan(zhour, zminute, 0);
DateTime netdttmoffset = netdttm.Subtract(timespan);
datetime.Value = netdttmoffset;
datetime.localDateTime = netdttmoffset.ToLocalTime();
datetime.localDateTimeSpecified = true;
I use a similar appraoch for the case where I use utcnow.
Problem i that I have limited testing possibilities due to hot-swapping being disbled in the environment where I have to develop my code. So I would like to be certainin about the formatting.
Thanx for your help.

I finally got it to work. My solution:
//declare the AX utcdatetime type from the cs class generate with:
//xsd C:\...\SharedTypes.xsd C:\..\AIFschema.xsd /Classes /Out:C:\location\of\csfile\
AxType_DateTime datetime = new AxType_DateTime();
//Ax store the time in GMT with an optional local time. My XML can have any timezone.
datetime.timezone = AxdEnum_Timezone.GMT_COORDINATEDUNIVERSALTIME;
//I set this to false as i am not interested in actually storing the local time. Plus AX fails over the formatting .net returns.
datetime.timezoneSpecified = false;
//{... left out code to retrieve the hours, minutes etc from my XML}
//declare the .net datetime variable with the values from the xml:
DateTime netdttm = new DateTime(year, month, day, hour, minute, second, millisecond, DateTimeKind.Utc);
DateTime netdttmoffset = new DateTime();
// (optional field) <zone>+01:00</zone>
if (message.Header.DateTime.Zone != null)
{
{... left out code to retrive zone offset info from xml}
TimeSpan timespan = new TimeSpan(zhour, zminute, 0);
netdttmoffset = netdttm.Subtract(timespan);
}
else //no zone, so datetime == GMT datetime.
{
netdttmoffset = netdttm;
}
datetime.Value = netdttmoffset;
datetime.localDateTime = netdttmoffset.ToLocalTime();
//do not output to xml, or AX will fail over this.
datetime.localDateTimeSpecified = false;
Result xml snippet as accepted by AX:
<MessageHeaderDateTime>2014-07-30T16:41:10.001Z</MessageHeaderDateTime>

I found this to be easier. If you want a particular datetime, say Jan 31, 2015 8:00 am, to be stored in AX, the .net code to make it happen would be
DateTime utcDateTime = new DateTime(2015, 1, 31, 8, 0, 0).ToUniversalTime();
var workerStartDate = new AxdExtType_HcmEmploymentStartDateTime
{
Value = utcDateTime
};
The XML generated would be would be <WorkerStartDate>2015-05-12T13:00:00Z</WorkerStartDate>, assuming you are 5 hours behind GMT on the computer that runs the .net code. The AX database will store the value 2015-05-12T13:00:00Z as well.

<dyn:StartDate>2014-06-22T00:00:00.000+02:00</dyn:StartDate>
This format always does the trick for me. (Notice the ms)

Get Current DateTime C# without hour

Hi I currently have a TimePicker. It returns an object TimeSpan.
What I need to do is to set a DateTimeOffset that is equal to current date plus the TimeSpan from the TimePicker.
How can I actually get the current DateTimeOffset.now that doesn't have a Time on it, only the Date so that I can add the offset to it.
Thanks

As in DateTime object you have a Date property, it returns date part without time (it means time is 00:00:00).
DateTime today = DateTimeOffset.Now.Date;
DateTime result = today + yourTimeSpan;
With this solution will lost Offset information (because Date is a DateTime). To keep it you just need to subtract time part:
DateTimeOffset now = DateTimeOffset.Now;
DateTimeOffset result = now - now.Time + yourTimeSpan;
Or with constructor:
DateTimeOffset now = DateTimeOffset.Now;
DateTimeOffset result = new DateTimeOffset(now.Date + yourTimeSpan, now.Offset);

Can you not just .Date it?
var a = DateTimeOffset.Now.Date;

try using:
DateTime.Today
instead of Now.

Convert datetime entered by user to UTC

The user enters a date and a time in separate textboxes. I then combine the date and time into a datetime. I need to convert this datetime to UTC to save it in the database. I have the user's time zone id saved in the database (they select it when they register). First, I tried the following:
string userTimeZoneID = "sometimezone"; // Retrieved from database
TimeZoneInfo userTimeZone = TimeZoneInfo.FindSystemTimeZoneById(userTimeZoneID);
DateTime dateOnly = someDate;
DateTime timeOnly = someTime;
DateTime combinedDateTime = dateOnly.Add(timeOnly.TimeOfDay);
DateTime convertedTime = TimeZoneInfo.ConvertTimeToUtc(combinedDateTime, userTimeZone);
This resulted in an exception:
The conversion could not be completed because the supplied DateTime did not have the Kind property set correctly. For example, when the Kind property is DateTimeKind.Local, the source time zone must be TimeZoneInfo.Local
I then tried setting the Kind property like so:
DateTime.SpecifyKind(combinedDateTime, DateTimeKind.Local);
This didn't work, so I tried:
DateTime.SpecifyKind(combinedDateTime, DateTimeKind.Unspecified);
This didn't work either. Can anyone explain what I need to do? Am I even going about this the correct way? Should I be using DateTimeOffset?

Just like all the other methods on DateTime, SpecifyKind doesn't change an existing value - it returns a new value. You need:
combinedDateTime = DateTime.SpecifyKind(combinedDateTime,
DateTimeKind.Unspecified);
Personally I'd recommend using Noda Time which makes this kind of thing rather clearer in my rather biased view (I'm the main author). You'd end up with this code instead:
DateTimeZone zone = ...;
LocalDate date = ...;
LocalTime time = ...;
LocalDateTime combined = date + time;
ZonedDateTime zoned = combined.InZoneLeniently(zone);
// You can now get the "Instant", or convert to UTC, or whatever...
The "leniently" part is because when you convert local times to a specific zone, there's the possibility for the local value being invalid or ambiguous in the time zone due to DST changes.

You can also try this
var combinedLocalTime = new DateTime((dateOnly + timeOnly.TimeOfDay).Ticks,DateTimeKind.Local);
var utcTime = combinedLocalTime.ToUniversalTime();

Join Date and Time to DateTime in C#

I am retrieving data from an iSeries where there is a separate date and time fields. I want to join them into a DateTime field in my C# project. I don't see a way to add just a time to a DateTime field. How would you suggest accomplishing this?

You can do this quite easily:
DateTime dateOnly;
DateTime timeOnly;
...
DateTime combined = dateOnly.Date.Add(timeOnly.TimeOfDay);
TimeOfDay returns a TimeSpan, which you then add to the date.
Edit (thanks to commenters below) - to be safe, use dateOnly.Date to ensure the date part only.

How are they being stored? Assuming that the date portion is being stored as a DateTime of midnight of the day in question and the time is a TimeSpan, you can just add them.
DateTime date = ...;
TimeSpan time = ...;
DateTime result = date + time;

You could easily construct a TimeSpan from your "time" field.
Once you have that, just do:
TimeSpan time = GetTimeFieldData();
dateField = dateField.Add(time);

Datetime date = new DateTime(Date1.Year, Date1.Month, Date1.Day, Time1.Hour, Time1.Minute, Time1.Second);

You can add a TimeSpan to a DateTime and write something like this.
// inside consuming function
ISeriesObject obj = getMyObject();
DateTime dt = getDate(obj) + getTime(obj);
private DateTime getDate(ISeriesObject obj)
{
//return a DateTime
}
private TimeSpan getTime(ISeriesObject obj)
{
//return a TimeSpan
}

My answer addresses joining two objects of DateOnly and TimeOnly in .NET 6:
DateOnly orderDate = ...
TimeOnly orderTime = ...
DateTime orderDateTime = orderDate.ToDateTime(orderTime);

This should do:
var output = date.Date + time.TimeOfDay;
or
var output = new DateTime(date.Year, date.Month, date.Day,
time.Hour, time.Minute, time.Second);
suppose that both variable date and time are both of Type DateTime

Note that adding the time to the date is not your biggest problem here. As #Reed Copsey mentioned, you just create a DateTime from the date and then .Add the time.
However, you need to make sure that the iSeries date and time (a Unix time most probably) are in the same representation as the .Net representation. Thus, you most probably need to convert it by adding it to a Jan 1, 1970 DateTime as well.

Cant you simply format the date part and time part as separate strings, then join them together? Then you can parse the string back to a DateTime object