I'm getting a curious issue when creating NSDates using dateWithTimeIntervalSince1970 on a simulator versus an iPhone device. I am simply translating an ISO8601 timestamp from an NSDate to milliseconds and then back to a NSDate.
NSDateFormatter *iso8601Formatter = [[NSDateFormatter alloc] init];
iso8601Formatter.dateFormat = TSMISO8601FormatString; // "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
NSDate startDate = [iso8601Formatter dateFromString: #"2014-03-19T09:46:00-06:00"];
long startTimeMilliseconds = [startDate timeIntervalSince1970] * 1000;
startDate = [NSDate dateWithTimeIntervalSince1970:(startTimeMilliseconds / 1000)];
When I run this on the simulator, I get the same date back but when I run it on my iPhone, I get back this. I'm really confused as to why I'm getting back a wildly different day
1970-01-25 20:31:23 +0000 // iPhone device results
I have checked to make sure that my timezone, date, and time format are the same on both just to make sure that this isn't the issue. And both are running iOS 7.1. I have also attempted to set both the locale and timezone for the NSDateFormatter without any success.
Any help would be appreciated
This:
long startTimeMilliseconds = [startDate timeIntervalSince1970] * 1000;
Should Be:
double startTimeMilliseconds = [startDate timeIntervalSince1970] * 1000;
Here's why,
The maximum long can be found with LONG_MAX and it will log:
2147483647
Your current time interval is:
1395243960000.000000
Long can't go big enough.
Related
I have a NSString (ex. "2011-04-12 19:23:39"), and what I did to format it to a NSDate was the following:
[inputFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSDate *date = [inputFormatter dateFromString:newDateString];
but what it outputs when I nslog the date is this:
2011-04-12 23:23:39 +0000
which is about 4 hours off. Is there something I missed? Possibly a time zone problem?
The answer in short, is the Date is being returned GMT unless specified otherwise. You can set your timezone to get the correct date. If you plan on using the date in the app to set anything ( like localNotification time or Event ) you will need to do something special with the date because if you set the date in the iPhone it will be set as GMT time and will be off by a few hours. ( in your case 4 hours ). I do this exact thing I just described in one of my apps.
I made a mess of trying to get this to work correctly without having the hours be off. It was a huge PITA to figure out but its working now. I have copied, pasted, and edited my code to share. Again, its messy but it works! The pickerChanged is getting its info from a UIDatePicker
Using the code below. To answer your question, you can stop at "destinationDate". That will return to you the corrected time for your current time zone. I just provided the extra incase you were trying to use the date in the Phone somewhere.
NOTE: for a quick example i put the Event reminder in the same function as the datepicker, you will NOT want to do that otherwise you will have alot of reminders set everytime the wheel scrolls in the datepicker.
The code is below.
- (void)pickerChanged:(id)sender
{
NSLog(#"value: %#",[sender date]);
NSDate* date= [sender date];
NSDateFormatter *formatter=[[[NSDateFormatter alloc]init]autorelease];
[formatter setDateFormat:#"MM/dd/yyyy hh:mm:ss a"];
[formatter setTimeZone:[NSTimeZone systemTimeZone]];
[formatter setTimeStyle:NSDateFormatterLongStyle];
NSString *dateSelected =[formatter stringFromDate:date];
NSString *timeZone = [dateSelected substringFromIndex:12];
NSTimeZone* destinationTimeZone = [NSTimeZone systemTimeZone];
//here we have to get the time difference between GMT and the current users Date (its in seconds)
NSInteger destinationGMTOffset = [destinationTimeZone secondsFromGMTForDate:date];
//need to reverse offset so its correct when we put it in the calendar
correctedTimeForCalendarEvent = destinationGMTOffset + (2*(-1*destinationGMTOffset));
//date to enter into calendar (we will use the correctedTimeForCalendarEvent to correct the time otherwise it will be off by a few hours )
NSDate * destinationDate = [[[NSDate alloc] initWithTimeInterval:destinationGMTOffset sinceDate:date] autorelease];
NSDate * dateForReminder = destinationDate;
// return destinationDate;
NSLog(#"value: %# - %#",destinationDate,dateForReminder);
//DO NOT put this code in this same function this is for a quick example only on StackOverflow
//otherwise you will have reminders set everytime the users scrolled to a different time
//set event reminder
//make sure to import EventKit framework
EKEventStore *eventDB = [[[EKEventStore alloc] init]autorelease];
EKEvent *myEvent = [EKEvent eventWithEventStore:eventDB];
NSString * eventTitle = [NSString stringWithFormat:#"%# - %#",app.dealerBusinessName,serviceOrComments.text];
myEvent.title = eventTitle;
//double check date one more time
NSLog(#"value: %#",destinationDate);
//set event time frame (1 hour) the "initWithTimeInterval" is where we account for the users timezone by adding the correctedTime from GMT to the calendar time ( so its not off by hours when entering into calendar)
myEvent.startDate = [[[NSDate alloc] initWithTimeInterval:correctedTimeForCalendarEvent sinceDate:destinationDate ]autorelease];
myEvent.endDate = [[[NSDate alloc] initWithTimeInterval:3600 sinceDate:myEvent.startDate]autorelease];
myEvent.allDay = NO;
//set event reminders 1 day and 1 hour before
myAlarmsArray = [[[NSMutableArray alloc] init] autorelease];
EKAlarm *alarm1 = [EKAlarm alarmWithRelativeOffset:-3600]; // 1 Hour
EKAlarm *alarm2 = [EKAlarm alarmWithRelativeOffset:-86400]; // 1 Day
[myAlarmsArray addObject:alarm1];
[myAlarmsArray addObject:alarm2];
myEvent.alarms = myAlarmsArray;
[myEvent setCalendar:[eventDB defaultCalendarForNewEvents]];
NSError *err;
[eventDB saveEvent:myEvent span:EKSpanThisEvent error:&err];
if (err == noErr) {
//no error, but do not show alert because we do that below.
}
}
NSDateFormatter use the current device timezone when it created the NSDate object. NSDate stores the date/time in GMT. Therefore by default NSLog will output the date/time in GMT+0. So, there's nothing wrong with your code. Now if you want to output the NSDate to your current timezone, your will have to use a NSDateFormatter object.
Your data and date formatter omit the TimeZone specifier. So something like this:
[inputFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ssZ"];
Would work - the Z is the timezone specifier and will parse both numeric offsets and timezone codes. Although in your case as your input date has no TimeZone information it won't work.
Your correct Time string should be like "2011-04-12 19:23:39 -0400" or "2011-04-12 19:23:39 EST "
Depending on where you get your date from, you should fix that to produce a fully qualified date if you can't do that, you will have to agree timezone offsets with the server or simply 'hard code' a timezone offset and add that number of seconds to your NSDate.
The date is being logged as a UTC date can be seen by the +0000 at the end. The date format you are using to parse the string assumes your local time zone which is presumably 4 hours behind UTC with daylight savings and the standard -5 hours.
Use -[NSDateFormatter setTimeZone:] to provide the date formatter with timezone information. You can use the local time zone, or if you have a fixed time zone associated with the date information, I recommend creating the timezone with the name (such as "America/East") rather than the abbreviation (such as "EST" or "EDT"), since the name does not force daylight savings into effect, but uses the correct daylight savings offset for that date in that timezone.
I want to present a date to the user of my app as "Today", "Yesterday" or as a formatted date (i.e. 27/05/2011). Is there a quick way to get "Today" or "Yesterday" based on a given NSDate? If not I can write the code myself, I am just curious if I am overlooking some simpler way than working out remaining hours manually.
If you just want to present date to your user, there is an option in NSDateFormatter right for that.
- (void)setDoesRelativeDateFormatting:(BOOL)b
Take a look at documentation for more information.
Check out this similar question: Compare NSDate for Today or Yesterday.
You make NSDate objects from today and yesterday, and then compare the first 10 characters of their description to the NSDate you're unsure of.
From the Date and Time Programming Guide:
NSTimeInterval secondsPerDay = 24 * 60 * 60;
NSDate *today = [[NSDate alloc] init];
NSDate *tomorrow, *yesterday;
tomorrow = [today dateByAddingTimeInterval: secondsPerDay];
yesterday = [today dateByAddingTimeInterval: -secondsPerDay];
[today release];
I have a NSString (ex. "2011-04-12 19:23:39"), and what I did to format it to a NSDate was the following:
[inputFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSDate *date = [inputFormatter dateFromString:newDateString];
but what it outputs when I nslog the date is this:
2011-04-12 23:23:39 +0000
which is about 4 hours off. Is there something I missed? Possibly a time zone problem?
The answer in short, is the Date is being returned GMT unless specified otherwise. You can set your timezone to get the correct date. If you plan on using the date in the app to set anything ( like localNotification time or Event ) you will need to do something special with the date because if you set the date in the iPhone it will be set as GMT time and will be off by a few hours. ( in your case 4 hours ). I do this exact thing I just described in one of my apps.
I made a mess of trying to get this to work correctly without having the hours be off. It was a huge PITA to figure out but its working now. I have copied, pasted, and edited my code to share. Again, its messy but it works! The pickerChanged is getting its info from a UIDatePicker
Using the code below. To answer your question, you can stop at "destinationDate". That will return to you the corrected time for your current time zone. I just provided the extra incase you were trying to use the date in the Phone somewhere.
NOTE: for a quick example i put the Event reminder in the same function as the datepicker, you will NOT want to do that otherwise you will have alot of reminders set everytime the wheel scrolls in the datepicker.
The code is below.
- (void)pickerChanged:(id)sender
{
NSLog(#"value: %#",[sender date]);
NSDate* date= [sender date];
NSDateFormatter *formatter=[[[NSDateFormatter alloc]init]autorelease];
[formatter setDateFormat:#"MM/dd/yyyy hh:mm:ss a"];
[formatter setTimeZone:[NSTimeZone systemTimeZone]];
[formatter setTimeStyle:NSDateFormatterLongStyle];
NSString *dateSelected =[formatter stringFromDate:date];
NSString *timeZone = [dateSelected substringFromIndex:12];
NSTimeZone* destinationTimeZone = [NSTimeZone systemTimeZone];
//here we have to get the time difference between GMT and the current users Date (its in seconds)
NSInteger destinationGMTOffset = [destinationTimeZone secondsFromGMTForDate:date];
//need to reverse offset so its correct when we put it in the calendar
correctedTimeForCalendarEvent = destinationGMTOffset + (2*(-1*destinationGMTOffset));
//date to enter into calendar (we will use the correctedTimeForCalendarEvent to correct the time otherwise it will be off by a few hours )
NSDate * destinationDate = [[[NSDate alloc] initWithTimeInterval:destinationGMTOffset sinceDate:date] autorelease];
NSDate * dateForReminder = destinationDate;
// return destinationDate;
NSLog(#"value: %# - %#",destinationDate,dateForReminder);
//DO NOT put this code in this same function this is for a quick example only on StackOverflow
//otherwise you will have reminders set everytime the users scrolled to a different time
//set event reminder
//make sure to import EventKit framework
EKEventStore *eventDB = [[[EKEventStore alloc] init]autorelease];
EKEvent *myEvent = [EKEvent eventWithEventStore:eventDB];
NSString * eventTitle = [NSString stringWithFormat:#"%# - %#",app.dealerBusinessName,serviceOrComments.text];
myEvent.title = eventTitle;
//double check date one more time
NSLog(#"value: %#",destinationDate);
//set event time frame (1 hour) the "initWithTimeInterval" is where we account for the users timezone by adding the correctedTime from GMT to the calendar time ( so its not off by hours when entering into calendar)
myEvent.startDate = [[[NSDate alloc] initWithTimeInterval:correctedTimeForCalendarEvent sinceDate:destinationDate ]autorelease];
myEvent.endDate = [[[NSDate alloc] initWithTimeInterval:3600 sinceDate:myEvent.startDate]autorelease];
myEvent.allDay = NO;
//set event reminders 1 day and 1 hour before
myAlarmsArray = [[[NSMutableArray alloc] init] autorelease];
EKAlarm *alarm1 = [EKAlarm alarmWithRelativeOffset:-3600]; // 1 Hour
EKAlarm *alarm2 = [EKAlarm alarmWithRelativeOffset:-86400]; // 1 Day
[myAlarmsArray addObject:alarm1];
[myAlarmsArray addObject:alarm2];
myEvent.alarms = myAlarmsArray;
[myEvent setCalendar:[eventDB defaultCalendarForNewEvents]];
NSError *err;
[eventDB saveEvent:myEvent span:EKSpanThisEvent error:&err];
if (err == noErr) {
//no error, but do not show alert because we do that below.
}
}
NSDateFormatter use the current device timezone when it created the NSDate object. NSDate stores the date/time in GMT. Therefore by default NSLog will output the date/time in GMT+0. So, there's nothing wrong with your code. Now if you want to output the NSDate to your current timezone, your will have to use a NSDateFormatter object.
Your data and date formatter omit the TimeZone specifier. So something like this:
[inputFormatter setDateFormat:#"yyyy-MM-dd HH:mm:ssZ"];
Would work - the Z is the timezone specifier and will parse both numeric offsets and timezone codes. Although in your case as your input date has no TimeZone information it won't work.
Your correct Time string should be like "2011-04-12 19:23:39 -0400" or "2011-04-12 19:23:39 EST "
Depending on where you get your date from, you should fix that to produce a fully qualified date if you can't do that, you will have to agree timezone offsets with the server or simply 'hard code' a timezone offset and add that number of seconds to your NSDate.
The date is being logged as a UTC date can be seen by the +0000 at the end. The date format you are using to parse the string assumes your local time zone which is presumably 4 hours behind UTC with daylight savings and the standard -5 hours.
Use -[NSDateFormatter setTimeZone:] to provide the date formatter with timezone information. You can use the local time zone, or if you have a fixed time zone associated with the date information, I recommend creating the timezone with the name (such as "America/East") rather than the abbreviation (such as "EST" or "EDT"), since the name does not force daylight savings into effect, but uses the correct daylight savings offset for that date in that timezone.
anyone know or can provide some example code relating to "timeIntervalSinceNow" method...
I need something like... time2(when app eneters foreground) - time1(when app enters background) = time3(the difference in times)... this is so i can use this number(pref in seconds) to calculate the time i have lost while the app has been in background !!
I am having trying trying to create the date objects, receive the object and display/use in a label....
Actually, to answer your original question, myles, you can use timeIntervalSinceNow.
In the statement below, inputDate has been initialized as an NSDate and set to some date (you could just try [NSDate *inputDate = [NSDate date]; to set the date at the current date and time.
NSTimeInterval timeToAlert =[inputDate timeIntervalSinceNow];
The next line is a way to put that NSTimeInterval into a string.
NSMutableString *timeinterval = [NSMutableString string];
[timeinterval appendFormat:#"%f",timeToAlert];
Finally, the app delegate class is typically where code can be written to handle coming in and out of background. Good luck!
timeIntervalSinceNow tells you the offset of an NSDate from the current time. You want timeIntervalSinceDate::
NSDate *appEnteredForeground = ...;
NSDate *appEnteredBackground = ...;
NSTimeInterval difference = [appEnteredBackground timeIntervalSinceDate: appEnteredForeground];
You can calculate the difference between two dates with the timeIntervalSinceDate: method:
//When app enters background:
self.backgroundDate = [NSDate date]; //this should be a property
//...
//When the app comes back to the foreground:
NSTimeInterval timeSpentInBackground = [[NSDate date] timeIntervalSinceDate:self.backgroundDate];
NSTimeInterval is simply a typedef for double, it's measured in seconds. [NSDate date] instantiates an NSDate object with the current date and time.
All,
This seems like such a simple thing, but I cannot find* the right method to create a UIDatePicker, in time mode, and have it initialized to a specific time. I don't want date -- just time (think alarm clock). I have created a NSDate object:
NSDate * date = [[NSDate alloc] initWithTimeIntervalSinceReferenceDate: (NSTimeInterval) delta];
pickerView = [[UIDatePicker alloc] init]; // which should be 'now' right?
pickerView.datePickerMode = UIDatePickerModeTime; // which creates just the clock
[pickerView setDate:date];
and in the first line, the interval (delta) is zero. It displays 7:00PM.
This has gotta be so simple that I'm missing it, but I can't find the right way -- anyone?
Thank you in advance!
:bp:
*yes, I have looked, but apparently not in the correct places :(
Take the time zone into account. You will get 0AM only if you are at UTC.
Thank you dkk -- I appreciate your help. The real answer was to not use a DatePicker, but to use a PickerView (w/o the date). That made things simpler and do-able.
Thanks again.
NSDate *date = [NSDate date];
date = [[NSCalendar autoupdatingCurrentCalendar] dateFromComponents:[[NSCalendar autoupdatingCurrentCalendar] components:NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay fromDate:date]];
date = [date dateByAddingTimeInterval:60 * 60 * 21];
pickerView.date = date;
The steps here with the date are
initialise date with the current date
get the date at midnight
add a time interval to the date (60 seconds * 60 minutes * hour). In this case 21 = 9pm
This works for UIDatePicker with datePickerMode of UIDatePickerModeTime & UIDatePickerModeCountDownTimer