I am trying to figure out the best way of letting the users set the internal DateTime value of the Portable Class Library based on some string parameter they provide. The string parameter has to be a simple format.
So, now I have some considerations.
Is specifying UTC Offset enough for getting the right DateTime
public static DateTime FromUtcOffset(string value)
{
var utcDateTime = DateTime.UtcNow;
var offSet = TimeSpan.Parse(value);
return utcDateTime + offSet;
}
Or is specifying the TimeZone has some advantage over UTC Offset
TimeZoneInfo someTimeZone = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");
DateTime convertTimeFromUtc = TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, someTimeZone);
My question is: What would be the right string parameter that can be taken from the user to let him decide what the value of DateTime would be?
Utc Offset
TimeZone
Or any other alternative that's less verbose.
Actually, it depends:
Do you work with network hosts, located in different time zones
Do you store time values for using them in future
Does your library work locally (hence, knows user's timezone)
1+2 basically mean if your time offset might change. If it not (the library is intended for local use only), get local time and don't care about the time offset. However, if the offset might change, usually storing "absolute" time in UTC format should be enough. To do this, you can:
Ask user for UTC time, not their local time
or
Ask for local time + offset (or get the offset from the local time zone, if possible)
Convert it to UTC time and store/process in UTC time
Provide output using local time (using the offset from 1. if it didn't change)
In 1 and 3 you will need a timezone to figure out the time offset. You don't need to know timezone if you already know the offset. Moreover, DateTime itself can store time offset information. It also can tell you if it stores local or UTC time (see DateTime.Kind Property).
Related
In c#, I do this
DateTime.Now.ToString("yyyy-dd-M--HH-mm-ss")
but it gets me the server time. However I also have the offset in this format for example "-04:00". How can I combine the offset to get the local time?
Thanks
If you mean that you want to get the server's system local time including offset, then use the DateTimeOffset.Now property. Then format it as desired.
DateTimeOffset.Now.ToString("yyyy-MM-dd HH:mm:ss zzz")
The zzz specifier produces the offset as a string in the ISO 8601 extended format, that you asked for.
If what you mean is you have a UTC offset from elsewhere and you want to apply it to the current UTC time from the server, then do the following instead:
TimeSpan offset = TimeSpan.Parse("-04:00");
DateTimeOffset now = DateTimeOffset.UtcNow.ToOffset(offset);
string result = now.ToString("yyyy-MM-dd HH:mm:ss zzz");
This takes the current server time, and applies the ToOffset function to adjust to the offset you provided.
Do keep in mind though that an offset is not the same as a time zone. The offset you have might be the one for the current date and time, or it might be for some other date and time in that time zone. For example, US Eastern Time is UTC-4 during daylight saving time, but UTC-5 during standard time. See "Time Zone != Offset" in the timezone tag wiki.
This worked.
DateTime.UtcNow.AddHours(DateTimeOffset.Parse("01/01/0001 00:00:00 -04:00").Offset.TotalHours).ToString("yyyy-dd-M--HH-mm-ss")
This should work
DateTime.UtcNow.AddHours(DateTimeOffset.Parse("01/01/0001 00:00:00 -04:00").Offset.TotalHours).ToString("yyyy-dd-M--HH-mm-ss",CultureInfo. InvariantCulture);
Need to add the directive
using System.Globalization;
I use this code to convert my UTC string Time with format "yyyy-MM-ddTHH:mm:ssZ" to date time . for example :
string PurchaseDate == "2017-12-12T14:29:26Z";
datetime dt = DateTime.ParseExact(PurchaseDate , "yyyy-MM-ddTHH:mm:ssZ", null);
i know that PurchaseDate time is UTC time (because of "Z"). dt return {12/12/2017 5:59:26 PM} that it is my local Time(client time zone). in other word DateTime.ParseExact convert PurchaseDate to my client time zone! my question is how this method know my client TimeZone ? is it recommend to use this for global application and show user time zone at all ??
Update My question:
sometime for implement timezone management in my global website i google it for possible souloution and I find this Use ful link :
How to display dates and times in clients timezone
after month i found we can use TimeZoneInfo.Local for finding cliend TimeZone !
so should i say that link is useless? I want to know if there is a simple way to find client time zone in dotNet BackEnd code so why this complex way is Used ??
... how this method know my client TimeZone?
It doesn't understand anything about a "client". It just has the local time of wherever the code is running. If the code is running on a user's desktop computer or mobile device, then it's the time zone of that device.
If the code is running on a server, then it uses the time zone of the server. You should avoid this in general, as the server's time zone is usually irrelevant to your application or users. This applies to TimeZoneInfo.Local as well.
If you want to parse your string as UTC DateTime, then you'll need to pass an argument that tells the parser not to convert to local time:
string PurchaseDate = "2017-12-12T14:29:26Z";
DateTime dt = DateTime.ParseExact(PurchaseDate, "yyyy-MM-ddTHH:mm:ssK",
CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind);
TimeZoneInfo tz = TimeZoneInfo.FindSystemTimeZoneById("...you'll need to decide...");
DateTime clientDateTime = TimeZoneInfo.ConvertTimeFromUtc(dt, tz);
In the above, I use DateTimeStyles.RoundtripKind, which says to evaluate the string for it's offset (Z in this case) and decide whether to use Utc, Local, or Unspecified kind on the resulting DateTime. Also note that you should use K in the format string, not Z.
A better approach would be to use DateTimeOffset instead of DateTime, in which case the Z will automatically set an offset of +00:00.
You'll still need to figure out what time zone to convert to, regardless of which approach you take. If you happen to be writing code that runs on the user's device, then you get the benefit of having TimeZoneInfo.Local predetermined for you. Otherwise you do not.
I'm consuming a Microsoft API which returns DateTimeOffset. The property has following documentation- This value is calculated based on current UTC time measured locally.
I want to compare this time with local server where my application is hosted. (So the DateTimeOffset is returned by Microsoft API and the place where I want to compare is on my server. These 2 can have different time zones).
When inspecting DateTimeOffset, Date & UTC property has same Date & Time and the Kind property is unspecified.
I'm currently using DateTimeOffset < DateTime.UtcNow for checking condition. Am I doing right?
You should use dateTimeOffset.LocalDateTime < dateTime.
.LocalDateTime method will convert the DateTimeOffset into your local time zone (with DateTimeKind.Local), so you can safely compare with your local DateTime.
You can get the offset time difference in the minutes using the below code
// Get the GMT time difference offset (This is your local time offset difference)
var timeOffsetinMiniut = DateTimeOffset.Now.Offset.TotalMinutes;
Now you can use add this offset in you local time to make it a UTC time.
var myNewDateTime = System.DateTime.Now.AddMinutes(timeOffsetinMiniut)
Now you can compare both time utc time and your new server time.
myNewDateTime < DateTime.UtcNow
Hope this will help you.
Thanks
My web service call to a third party applications returns the date,time zone and timezone_offset values. I need to add this to a calendar in Asp.net application. What is the best way to combine this together so that my date object understands that its from Eastern time zone?
<start_date>2014-11-17 19:00:00</start_date>
<timezone>America/New_York</timezone>
<timezone_offset>GMT-0500</timezone_offset>
Since you have the offset too, you can use DateTimeOffset.Parse() to get the DateTimeOffset. From there, you can read the DateTime property. The output dt variable will have 2014-11-17 7:00:00 PM with DateTimeKind property set to "Unspecified"
var dtOffset = DateTimeOffset.Parse("2014-11-17 19:00:00-0500", CultureInfo.InvariantCulture);
var dt = dtOffset.DateTime;
A DateTimeOffset represents a point in time. Usually, its relative to UTC. So, it is a natural structure to initially parse the fields that you have.
If you want a reference to the same datetime in UTC, you can use this. Here the output dt variable will have 2014-11-18 12:00:00 AM with DateTimeKind property set to "Utc"
var dt = DateTime.Parse("2014-11-17 19:00:00-0500", CultureInfo.InvariantCulture).ToUniversalTime();
If you don't have the offset but just have the timeZoneId, you can still do it but you need NodaTime for that.
I'll focus on this part of the question:
What is the best way to combine this together so that my date object understands that its from Eastern time zone?
There is no data type built in to .NET that can sufficiently do that. The DateTimeOffset type associates with a particular offset, such as the -05:00 or -04:00 that might be in use by the Eastern time zone (depending on the date). But those same offsets might also be sourced from some other time zone entirely. A time zone has one or more offsets, but an offset isn't a time zone itself.
Fortunately there are solutions. There are two options to consider:
You could pair a DateTimeOffset with a TimeZoneInfo object. When storing or transmitting these, you would only send the full DateTimeOffset along with the Id of the time zone.
The Noda Time library is a much more effective way to work with date and time, especially when it comes to time zone concerns. It contains a type called ZonedDateTime that already combines a date, time, offset, and time zone. It can also be used to work with IANA time zone identifiers, such as the "America/New_York" time zone you specified in the question.
I get date data from a user. That data is a date (e.g. 4/23/2011) and an hour (0 - 23), representing the time. This date/time that the user selects is a local time.
I need to convert this to a UTC DateTime. I have their GMTOffset for their location. How can I do this?
You should work with the DateTimeOffset structure, specifically, the constructor that takes the DateTime and the TimeSpan that represents the offset.
From there, conversions to/from UTC are a breeze, as the offset is embedded in the structure and not dependent on local system settings.
Note, even though not commonly adhered to, it is recommended to work with DateTimeOffset most of the time, as opposed to DateTime (see the note under the section titled "The DateTimeOffset Structure").
var utcDateTime =
new DateTimeOffset(userDateTime, TimeSpan.FromHours(userUtcOffset)).UtcDateTime;
Of course you can use TimeSpan differently if the GMT offset has minutes / fractions of an hour.
Just use the DateTime.ToUniversalTime in C#, will that do what you want?