I am trying to convert my device current time into Zone (America/New_york)
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithName:#"America/New_York"]];
NSDate *start = [NSDate date];
start now has the device current time in IST. How can I convert it into zone 'America'
I planned to do the below
start = [dateFormatter dateFromString:<start date String>];
A Day is categorised into 3 divisions based on a time period.
Say 08:00 - 15:00 AS PHASE1
15:00 - 17:00 AS PHASE2
17:00 - 20:00 AS PHASE3
20:00 - 08:00 AS TRANSITION PHASE and can be ignored.
Am just taking device's date and append the time string to identify in which phase it is.
Example: Indian Time is 05-FEB-2014 01:25 AM (Device Date)
Considering 15:00 as first cutoff.. I append the '05-FEB-2014' to 15:00 and digest it as American timezone.. Which resolves and gives me 06-FEB-2014 02:30 IST(Cut off Date).. So the difference between the both days goes greater than one day!
My expected result could be take device time also in American Timezone and compare with the compare with the nearest cut off time.
NSDate does not have a time zone. It's a single time reference that's valid anywhere. It's basically just an object wrapper for NSTimeInterval-- all it stores is the number of seconds since a reference date. Time zones only apply when converting to/from user-visible strings.
You can get a user-visible string from your date formatter as
NSString *localizedDateString = [dateFormatter stringFromDate:start];
But converting NSDate to a particular time zone is not a meaningful goal. There's no time zone on NSDate, so it's not a conversion that can be applied.
Date of new york :
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:#"America/New_York"];
[dateFormatter setTimeZone:timeZone];
NSString *dateString = [dateFormatter stringFromDate:[NSDate date]];
NSLog(#"Date : %#", dateString);
Date of all zones :
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSArray *timeZoneNames = [NSTimeZone knownTimeZoneNames];
for (NSString *name in timeZoneNames) {
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:name];
[dateFormatter setTimeZone:timeZone];
NSString *dateString = [dateFormatter stringFromDate:[NSDate date]];
NSLog(#"timeZone abbreviation : %#\nName : \"%#\"\nDate : %#\n\n", [timeZone abbreviation], name, dateString);
}
See the stringFromDate Method in the dateformatter. You pass in an NSDateand it converts to the specified format.
UPDATE: Here is how you set the current time zone [dateFormatter setTimeZone:[NSTimeZone systemTimeZone]];
https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSDateFormatter_Class/Reference/Reference.html
Related
I am working on an application that creates alerts with calendar. I can correctly set alarms on correct dates. For example, I set an alarm for 4th of May 2017 1 PM.
When, I try to get the calendar event it returns me some other date in UTC.
As you can see, it returns me 10 AM on same day with UTC. I am wondering how can I get the exact date when I try to get it from calendar.
You just need to convert UTC to your local timezone.
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
NSDate *date1 = [dateFormatter dateFromString:#"2017-05-04 10:00:00"];
// change to a readable time format and change to local time zone
[dateFormatter setDateFormat:#"MM/dd/yyyy hh:mm a"];
[dateFormatter setTimeZone:[NSTimeZone localTimeZone]];
NSString *strCurrentLocalTimezoneDate = [dateFormatter stringFromDate:date1];
Date always takes current time zone until we changed other.If we print the Date it might be showing different but actually it takes current.
// except this code you may have to set timeZone as well.
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:#"MMM-dd-yyyy"];
NSDate *now = [[NSDate alloc] init];
NSString *dateString = [format stringFromDate:now];
NSLog(#"%#",dateString);
I am doing a prayer alarm app and i want to compare my current time with fetched time, but when i am getting my current time, it has some time difference always as shown;
// getting today's date string
NSDate *today = [NSDate date];
NSDateFormatter *dateFormatterToday = [[NSDateFormatter alloc] init];
dateFormatterToday.timeZone = [NSTimeZone localTimeZone];
[dateFormatterToday setDateFormat:#"yyyy-MM-dd HH:mm a"];
NSString *currentDateTimeString = [dateFormatterToday stringFromDate:today];
// converting today's date string to NSDATE
NSDateFormatter *dateFormatterTodayFinal = [[NSDateFormatter alloc] init];
[dateFormatterTodayFinal setDateFormat:#"yyyy-MM-dd HH:mm a"];
dateFormatterTodayFinal.timeZone = [NSTimeZone localTimeZone];
NSDate *dateTodayFinal = [dateFormatterTodayFinal dateFromString:currentDateTimeString];
Here currentDateTimeString, which is in string format showing my current time as :
2016-01-11 17:52 PM (which is correct one)
but dateTodayFinal, which is in Date format shows:
2016-01-11 07:22:00 +0000
I have tested with different timezones, but the issue persist, please help some one. Thank you.
The second example is missing a stringFromDate call so the description method is probably used which uses it's own format, not the dateFormatterToday formatter. Also missing are the printing calls so we can only guess.
Add:
NSString *dateTodayFinalTimeString = [dateFormatterToday stringFromDate:dateTodayFinal];
NSLog(#"dateTodayFinalTimeString: %#", dateTodayFinalTimeString);
Output:
dateTodayFinalTimeString: 2016-01-11 07:57 AM
NSDate doesn't have any information about the timeZone, when you hover over the NSDate in xCode it will show you the time is in UTC.
If you want to convert the time back and forth, this information (timezone) has to be in the string you want to parse as well and set the timezone back to UTC:
NSDate *today = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.timeZone = [NSTimeZone localTimeZone];
[dateFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss Z"];
NSString *currentDateTimeString = [dateFormatter stringFromDate:today];
// converting today's date string to NSDATE
//
// NSDateFormatter *dateFormatterTodayFinal = [[NSDateFormatter alloc] init];
// [dateFormatterTodayFinal setDateFormat:#"yyyy-MM-dd HH:mm:ss Z"];
dateFormatterToday.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
NSDate *dateTodayFinal = [dateFormatter dateFromString:currentDateTimeString];
Also have a look at the docs.
I asked a question not too long ago about timezone and I was using EST. Users suggested me to use EDT. I want to know why I should use one or the other because they both print the same time for me. Here is the code to better illustrate what I mean.
NSDate *today = [NSDate date];
NSDateFormatter *edtDf = [[NSDateFormatter alloc] init];
[edtDf setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"EDT"]];
[edtDf setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSString *stringDate = [edtDf stringFromDate:today];
NSLog(#"The EDT is %#", stringDate);
NSDate *today1 = [NSDate date];
NSDateFormatter *estDf = [[NSDateFormatter alloc] init];
[estDf setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"EST"]];
[estDf setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSString *stringDate1 = [estDf stringFromDate:today1];
NSLog(#"The EST is %#", stringDate1);
They may print different things depending on the time of year (since time of year determines whether Daylight Saving Time is active).
Don't use EST or EDT. Use US/Eastern or America/New_York:
NSTimeZone *tz = [NSTimeZone timeZoneWithName:#"US/Eastern"];
// or
NSTimeZone *tz = [NSTimeZone timeZoneWithName:#"America/New_York"];
These time zones adjust for Daylight Saving Time at the correct times of the year.
This question already has an answer here:
NSDateFormatter and Time Zone issue?
(1 answer)
Closed 8 years ago.
-(NSTimeInterval)convertStringToDate:(NSString *) date {
NSString *dateString = date;
NSLog(#"dateString = %#", dateString);
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"dd-MM-yyyy hh:mm a"];
[dateFormatter setLocale:[NSLocale currentLocale]];
NSDate *date1 = [[NSDate alloc] init];
date1 = [dateFormatter dateFromString:dateString];
NSLog(#"dateFromString = %#", date1);
NSString *displayDate = [dateFormatter stringFromDate:date1];
NSLog(#"displayDate = %#", displayDate);
return [date1 timeIntervalSince1970];
}
Why I am getting NSTimeInterval with wrong timezone?
You need to read up on the internal representation of NSDates. An NSDate is saved as the number seconds since midnight on 1 Jan, 1984 GMT (The Mac OS X "epoch date") . It represents an instant in time anywhere on the earth, but using a date in GMT as it's "zero date". To display it, you need to convert it to your local time zone.
NSDate has a couple of methods to convert a date to a number: timeIntervalSince1970, which converts an NSDate to the internet standard, which is the number of seconds since Midnight 1 Jan 1970 (The UNIX "epoch date"), and timeIntervalSinceReferenceDate, which converts to the number seconds since the Mac Epoch date.
If you display a date in NSLog:
NSLog(#"Date = %#", someNSDate);
It will be displayed in GMT.
Honestly, it's unclear what you're asking and my best guess is that you just don't understand the classes at play. I've annotated your code in the hope of aiding your comprehension.
Key point: NSDate does not have a time zone. It's an opaque time stamp.
-(NSTimeInterval)convertStringToDate:(NSString *) date {
// log the input string
NSString *dateString = date;
NSLog(#"dateString = %#", dateString);
// create an object that can apply a locale and a time zone in order to
// convert an NSDate to an NSString and vice versa
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"dd-MM-yyyy hh:mm a"];
[dateFormatter setLocale:[NSLocale currentLocale]];
// get a date that represents exactly now, for no reason as it's about
// to be thrown away
NSDate *date1 = [[NSDate alloc] init];
// convert to the NSDate that represents the given string.
date1 = [dateFormatter dateFromString:dateString];
// log the converted date. BECAUSE NSDATE DOES NOT HAVE A TIME ZONE,
// it will arbitrarily be displayed in UTC. Because it has to be
// displayed in something
NSLog(#"dateFromString = %#", date1);
// convert date1 back into a printable date; this will again apply
// a time zone and locale
NSString *displayDate = [dateFormatter stringFromDate:date1];
NSLog(#"displayDate = %#", displayDate);
// query the date for "The interval between the date object and
// January 1, 1970 at 12:00 a.m. GMT."; return that
return [date1 timeIntervalSince1970];
}
I was trying to format a time from GMT+7 to GMT+3:
I am building an app with a world clock in specific country (the user will be at the GMT+7and I want to represent the GMT+3 time )
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setLocale:[NSLocale currentLocale];
NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:118800];
NSLocale *USLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US"];
[dateFormatter setLocale:USLocale];
NSLog(#"Date for locale %#: %#",
[[dateFormatter locale] localeIdentifier], [dateFormatter stringFromDate:date]);
I looked deep into NSDate class reference but I didn't understand how to make it.
Please if someone can help me I will be grateful.
There is 2 important parameters that works separately: Time and Time Zone.
e.g: Vietnam uses GMT+7
If I know that the time in Vietnam is 9:00 AM, then GMT time is 2:00 AM.
When you get the Date from your device you are getting Time and Time Zone: YYYY-MM-DD HH:MM:SS ±HHMM. Where ±HHMM is a time zone offset in hours and minutes from GMT.
Usually you are only using time. However with NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:#"GMT"] you can tell the NSDateFormatter that you want the GMT time related to your local Time Zone. So, with:
NSDateFormatter *dt = [[NSDateFormatter alloc] init];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:#"GMT"];
[dt setTimeZone:timeZone];
You can get the GMT date of your local time zone date.
So, If you have GMT+7: 9:00 AM and you want to print out GMT+3: 5:00 AM, you have 3 possibilities:
NSDate *localDate = [NSDate date];
OPTION 1
Add a time interval of -4 hours:
NSTimeInterval secondsInFourHours = -4 * 60 * 60;
NSDate *dateThreeHoursAhead = [localDate dateByAddingTimeInterval:secondsInFourHours];
NSDateFormatter *dt = [[NSDateFormatter alloc] init];
[dt setDateFormat:#"h:mm a"];
NSLog(#"GMT+7(-4) = %#", [dt stringFromDate:dateThreeHoursAhead]);
This is the easiest way to do it. If you are always at GMT+7 and you need GMT+3, this is a time interval of -4 hours.
OPTION 2
Set the time to GMT time zone and then add a +3hours time interval. The easiest way to do it is to add the 3 hours first and then move the time to GMT:
NSTimeInterval secondsInThreeHours = 3 * 60 * 60;
NSDate *dateThreeHoursAhead = [localDate dateByAddingTimeInterval:secondsInThreeHours];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:#"GMT"];
[dateFormatter setTimeZone:timeZone];
[dateFormatter setDateFormat:#"h:mm a"];
NSString *date = [dateFormatter stringFromDate:dateThreeHoursAhead];
NSLog(#"GMT+3 = %#", date);
OPTION 3
This is the better option. GMT+3 is EAT (East Africa Time) you can set your time zone to EAT with: [NSTimeZone timeZoneWithName:#"EAT"]
NSDateFormatter *dt = [[NSDateFormatter alloc] init];
[dt setDateFormat:#"h:mm a"];
NSTimeZone *timeZone = [NSTimeZone timeZoneWithName:#"EAT"];
[dt setTimeZone:timeZone];
NSLog(#"EAT = %#", [dt stringFromDate:localDate]);
Option 3 is always retrieving GMT+3
An example code here.