I'm developing an app for iPhone that uploads pictures to a webserver. These pictures have the time of when they were taken in the filename. Since they can be taken from anywhere in the World, I have to keep attention to timezones and DST. I thought I can use CFAbsoluteTimeGetCurrent, that shouldn't be localized ([NSDate date] returns the localized version of time, with or without "AM", "PM", "p.m." or any other variant... for example it returns Arabian characters, if your phone is set in arabic language!).
So, can you suggest me a function to convert CFAbsoluteTimeGetCurrent to a "MySQL like" date, something like "2011-11-03 14:12:10"?
My second question is: what about timezones and daylight saving? CFAbsoluteTimeGetCurrent always returns an UTC date, no matter how the iPhone timezone is set? Is it always DST-free?
Of course I know that the local iPhone date/time could be wrong, but milliseconds-precision is not important for my application :)
Thank you in advance!
What on earth do you mean by
([NSDate date] returns the localized version of time, with or without "AM", "PM", "p.m." or any other variant... for example it returns Arabian characters, if your phone is set in arabic language!).
[NSDate date] returns an NSDate* object. I'm assuming what you really mean is the output of -[NSDate description] returns a string localized in the user's current locale, but then the question is, why are you depending on the output of -[NSDate date]? If you need to format a date a certain way, you should use an NSDateFormatter.
CFAbsoluteTime represents a moment in time, independent of time zones or localization settings. If you want to format a date (i.e. an NSDate object) you should look at NSDateFormatter, which lets you specify the exact format and localization (if any) of the output string. (If you need to work at the Core Foundation level, CFDateFormatter does the same thing.)
Related
NSDate *createDate = [NSDate dateWithTimeIntervalSince1970:1376460694.103];
NSLog(#"createDate %#",createDate);
I am using the above code to get the current date and time,when I put break point at createDate,It shows correct time stamp value,but NSLog(#"createDate %#",createDate) statement is printing the date as 2013-08-14 06:11:34 +0000.
How to get the correct result?
The date is correct. When printing to the console the description of the date is used and that uses your system locale so it applies your time zone to the date before printing.
When you want to display the time you need to use a date formatter to convert the date into a string. The important part is setting the locale / time zone that the formatter uses.
Take a read of this and this.
I set the date variable
Dim myDate as Date
myDate = #5/15/2013#
Does this work always at runtime, no matter what is the system locale settings?
According to the MSDN documentation:
You must enclose a Date literal within number signs (# #). You must specify the date value in the format M/d/yyyy, for example #5/31/1993#. This requirement is independent of your locale and your computer's date and time format settings.
The reason for this restriction is that the meaning of your code should never change depending on the locale in which your application is running. Suppose you hard-code a Date literal of #3/4/1998# and intend it to mean March 4, 1998. In a locale that uses mm/dd/yyyy, 3/4/1998 compiles as you intend. But suppose you deploy your application in many countries. In a locale that uses dd/mm/yyyy, your hard-coded literal would compile to April 3, 1998. In a locale that uses yyyy/mm/dd, the literal would be invalid (April 1998, 0003) and cause a compiler error.
So, the answer to your question is YES, it will always work at runtime, and NO, you do not need to change this for the locale settings of the computer.
Do keep in mind that date literals are somewhat frowned upon. They are supported in VB.Net as a backwards-familiarity thing from VB6. They don't even exist in other .Net languages like C#. If you have to hard-code a specific date, you are much better off using DateTime with separate parameters, such as:
Dim myDate as DateTime
myDate = new DateTime(2013,5,15)
Also note that Date is just a VB.Net alias to System.DateTime, again there for backwards familiarity from VB6. It doesn't matter which you use, they mean the same thing.
No, that does not work in a country such as Canada where the standard is dd/MM/yyyy. The best way to globalize your application would be to use DateTime.ParseExact and/or DateTime.TryParseExact
Dim tempdate As DateTime
tempdate = DateTime.ParseExact("05/20/2013", "MM/dd/yyyy", Globalization.CultureInfo.InvariantCulture)
guys
I have two question to ask, they're easy, but bothering me for a while.
I access my .NET test WebService, and it return two parameters to me.
One is a date data just like "/Date(1332399761677+0800)/", and I dont know
how to format it to the normal date format.
Two is a NSString data looks like "12000.00000",and I want to change it to
the format like this:"12000.00".
So,please help me with this two problems. Thank you in advance.
1332399761677 looks like a Unix date, so if you grab that part of the string, use NSString doubleValue to turn it into a double, then use NSDate dateWithTimeIntervalSince1970:, you should be able to get a date. +0800 looks like a timezone, but you wouldn't need the timezone to get the date given a Unix date: 1332399761677 would specify a specific point in time, irrespective of timezones.
As for "12000.00000", you would use doubleValue to make it into a double, make an NSNumberFormatter with its maximumFractionDigits and minimumFractionDigits set to 2, then use stringFromNumber:.
I have an app where I set time zones for various cities around the globe. I have no problem doing this and it works great. When the app first loads, it finds your current location (lat & long) and sets the time zone using the device default time zone. I need to return the default time zone in a string, so I can display it. I don't want "GMT" or "EDT", I would like it in the format of "America/New_York" or 'Europe/London". Any ideas?
It sounds like you want this:
NSString *timeZoneName = [[NSTimeZone localTimeZone] name];
That returns "America/New_York" for me, here in the EST time zone.
Or given any NSTimeZone *tz you can get its [tz name], which is the conventional name you are looking for (e.g. "Asia/Tokyo" or "Europe/London".
Look at +[NSTimeZone knownTimeZoneName] for a list of possible names.
I hope that helps.
I don't think there is an object that automatically correlates the time zone to a physical place.
I see you've tagged this objective-c, but in C# you could do something simple like this:
public Enum TimeZone
{
[Description("New York")]
EDT,
[Description("Los Angeles")]
PST
}
public static string GetDescription(Enum value)
{
FieldInfo fi= value.GetType().GetField(value.ToString());
DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
return (attributes.Length>0)?attributes[0].Description:value.ToString();
}
i'm not sure how easily portable this is to objective-c, and it does require using the reflection library in C#.
Well, you're making the assumption that EDT is the same time zone as America/New_York. It isn't. :) Yes, they're the same UTC offset, but as far as your system is concerned, they are defined independently. There's no strong association between them that Cocoa knows about.
As well, if the user gives you EDT, do you return New_York? Toronto? Panama? There's not a 1:1 correspondence. Oh, and: EDT isn't even unique to a single UTC offset. Australian Eastern Daylight Time is also abbreviated EDT, I'm told by the Cocoa docs.
There is a [NSTimeZone abbreviationDictionary] map between abbreviations and long names, but again, they're arbitrarily chosen when there's more than one association (such as New York and Panama.)
What is it you're trying to accomplish in a broader sense? What's your goal? Tell us and we may be able to suggest an alternate way to achieve it. :)
I'm sorry to make my first question here a bit of a simple one -- I've spent a day reading the NSLocale and NSCalendar class descriptions but I couldn't see if this was possible.
I have a UIDatePicker in the UIDatePickerModeDateAndTime mode. It is currently displaying date and time according to the user's locale, which is the default behavior.
I would like to be able to offer the option to show the UIDatePicker in either 12-hour or 24-hour time format. Detecting which time format the user is currently using isn't a problem, but I'm not clear on how to change just the time format of UIDatePicker without entirely throwing out the user's locale settings (since the picker also displays the localized days of the week and months). UIDatePicker supports setting its locale and setting its calendar.
So, question one is whether this is something I should be trying to do via NSLocale or NSCalendar, and question two is if anyone can recommend a way to isolate the time format without throwing out the rest of the user's locale settings.
Thanks for any suggestions.
This is not the answer you are looking for, but in Cocoa you could create an NSDateFormatter and attach it to an NSDatePicker (which is an NSControl) using setFormatter. Unfortunately the equivalent iPhone class (UIControl) does not support this yet. I raised a bug with Apple about it and this is a known issue, although they wouldn't tell me if/when they plan to fix/enhance it.
OK, after reading the last two years' worth of others asking the same question here, it seems that there is no way to do this since the UIDatePicker uses the user's country setting instead of the user's locale setting, and that can't be overridden programmatically. I filed a bug.
I have solved this problem by using the user input of AM/PM by initializing another variable as a string of either AM or PM based upon the 12 hour format. The new hour in 24 hour format is put into NSCalendar. To wit:
var hra = 1//ENTER INITIAL HOUR (HH)
var dna = "PM"//ENTER "AM" OR "PM"
if hra <= 12 && dna == "PM"{
hra = hra + 12
}
The variable hra now takes the value of the 24 hour format.