I have a calendar app, in which I highlight current date,
I have followed the following steps, at present my device time is 11:59 am,
Indian time zone, I change it to first 9.am, then I change time zone to san jose ,
I get time as 25th june 9.34 pm, now in device calendar it shows 25th june, but
in my app it still shows 26th june.
I am getting current date this way
-(void)initialize
{
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
[gregorian setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
NSDateComponents *weekdayComponents = [gregorian components:(NSDayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSMinuteCalendarUnit)fromDate:[NSDate date]];
NSInteger day = [weekdayComponents day];
NSInteger month = [weekdayComponents month];
NSInteger year = [weekdayComponents year];
[m_dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
m_dateFormatter.dateFormat = #"dd/MM/yyyy";
NSDateComponents *timeZoneComps=[[NSDateComponents alloc] init];
[timeZoneComps setDay:day];
[timeZoneComps setMonth:month];
[timeZoneComps setYear:year];
[timeZoneComps setHour:00];
[timeZoneComps setMinute:00];
[timeZoneComps setSecond:01];
m_currentDate = [gregorian dateFromComponents:timeZoneComps];
}
So, I need your help in this regard.
I think that [NSTimeZone systemTimeZone] will always give you the current timezone as detected (or set) by the device. Since the timezone is cached in your app you can also call [NSTimeZone resetSystemTimeZone] to make sure that the info is up to date. So, in your code:
[NSTimeZone resetSystemTimeZone];
[m_dateFormatter setTimeZone:[NSTimeZone systemTimeZone]];
Related
I am trying to fetch images from photo library within the range of two dates and I am getting the images successfully. Using PHAsset Library
Now the problem is that am not able to get images between two times of the same day like between 12:10PM to 12:30PM
Using below code
NSDate *startDate = [self getDateForDay:30 andMonth:9 andYear:2016 andHour:12 andMinute:10 andSecond:0];
NSDate *endDate = [self getDateForDay:30 andMonth:9 andYear:2016 andHour:12 andMinute:30 andSecond:0];
--
-(NSDate*) getDateForDay:(NSInteger) day andMonth:(NSInteger) month andYear:(NSInteger) year andHour:(NSInteger) hour andMinute:(NSInteger) minute andSecond:(NSInteger) second{
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setDay:day];
[comps setMonth:month];
[comps setYear:year];
[comps setHour:hour];
[comps setMinute:minute];
[comps setSecond:second];
NSCalendar* gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
[gregorian setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"GMT"]];
NSDate *date = [gregorian dateFromComponents:comps];
return date;
}
-- And passing those dates to below method to get images
PHFetchResult *result = [self getAssetsFromLibraryWithStartDate:startDate andEndDate:endDate];
Dates and time coming correct when i print in log but not getting images
How to solve this problem ?
The date created here would be in UTC timezone and yours may vary. Which is why the predicate may not return you correct results.
Make sure you have set the timezone of calendar to your system timezone before creating a date from it like:
NSCalendar* gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
[gregorian setTimeZone: [NSTimeZone systemTimeZone]];
NSDate *date = [gregorian dateFromComponents:comps];
That will create the date in your local timezone and generate correct results.
I know there's a few questions already on this but I keep running into the same error regardless of what I do to my code. I am working in the simulator, I have location set to my long/lat. When I try to convert the current date to zero hours, minutes, seconds I always get this result:
2015-07-10 08:53:19.868 xxxxxxxxxxxxxxxxx[2184:7462272] Today at start of day:2015-07-10 04:00:00 +0000
Here's my code:
NSDate* today = [[NSDate alloc] init];
NSCalendar* currentCalendar = [NSCalendar currentCalendar];
NSDateComponents* dateComponents = [currentCalendar components:NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitYear fromDate:today];
NSInteger thisMonth = [dateComponents month];
NSInteger thisDay = [dateComponents day];
NSInteger thisYear = [dateComponents year];
NSDateComponents* dayComponents = [[NSDateComponents alloc] init];
[dayComponents setDay:thisDay];
[dayComponents setMonth:thisMonth];
[dayComponents setYear:thisYear];
NSDate* todayAtMidnight = [currentCalendar dateFromComponents:dayComponents];
NSLog(#"Today at start of day:%#", todayAtMidnight);
Even if add
[dayComponents setHour:0]; the hour still comes out as 4.
What am I doing wrong?
To get the beginning of today you can use
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
fromDate:[NSDate date]];
[calendar setTimeZone:[NSTimeZone timeZoneWithName:#"GMT"]];
NSLog(#"date %#", [calendar dateFromComponents:components]);
Make sure you have the correct timezone
2015-07-10 04:00:00 +0000 is UTC, not your local timezone.
To display it in your local timezone, use an NSDateFormatter:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = #"yyyy-MM-dd HH:mm";
[dateFormatter setTimeZone:[NSTimeZone systemTimeZone]];
NSLog([dateFormatter stringFromDate:todayAtMidnight]);
Use NSDateFormatter as follow because system timezone is UTC:
NSDateFormatter * formatter = [[NSDateFormatter alloc] init];
[formatter setTimeZone:[NSTimeZone timeZoneWithName:#"GMT"]];
[formatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSDate * curDate = [formatter dateFromString:[NSDate date]];
Then you'll get 2015-07-10 00:00:00.
I am trying trying to get a create an object of NSDate this way
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
// [gregorian setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
NSDateComponents *weekdayComponents = [gregorian components:(NSDayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSMinuteCalendarUnit)fromDate:[NSDate date]];
NSInteger day = [weekdayComponents day];
NSInteger month = [weekdayComponents month];
NSInteger year = [weekdayComponents year];
NSDateComponents *timeZoneComps=[[NSDateComponents alloc] init];
[timeZoneComps setDay:day];
[timeZoneComps setMonth:month];
[timeZoneComps setYear:year];
[timeZoneComps setHour:00];
[timeZoneComps setMinute:00];
[timeZoneComps setSecond:01];
m_currentDate = [gregorian dateFromComponents:timeZoneComps];
When I log the currentDate, I get this
"2014-07-07 06:00:01 +0000"
If I save this to plist I get this
07-Jul-2014 11:30:01 am
If I use "UTC" as the time zone
I get it as
"2014-07-07 00:00:01 +0000"
and inside plist it shows as
07-Jul-2014 5:30:01 am
I am not understanding what is going on, Can anybody help me out with this
I want to know, if I dont set any timeZone what timeZone will be used?
Do we need to explicitly set UTC as timeZone or we need to use systemTimeZone.
The thing you need to realise about NSDate is that there is no such thing as day, week, month, year, timezone, etc...
An NSDate is purely a point in time. It has no information about what time zone it is etc...
Effectively it is just a number. You can think of it as using UTC if that helps.
The classes that give you things like time zone are NSCalendar, NSDateFormatter, etc...
I'm guessing you're in a timezone of UTC+6? Thats why when you create a date with 00:00:01 and you log it out then it displays as 06:00:01.
This is nothing to do with the NSDate. What you are seeing in the console is a string. It is a representation of the date object using the default time zone (your own).
I'd have to see you code for saving to a plist but I suspect this is the same problem. You are saving something and assuming it is using a particular time zone when in reality it isn't.
I have created a calendar in my app, using the date object this way:
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *weekdayComponents = [gregorian components:(NSDayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSMinuteCalendarUnit)fromDate:[NSDate date]];
NSInteger day = [weekdayComponents day];
NSInteger month = [weekdayComponents month];
NSInteger year = [weekdayComponents year];
m_dateFormatter.dateFormat = #"dd/MM/yyyy";
[gregorian setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
NSDateComponents *timeZoneComps=[[NSDateComponents alloc] init];
[timeZoneComps setDay:day];
[timeZoneComps setMonth:month];
[timeZoneComps setYear:year];
[timeZoneComps setHour:00];
[timeZoneComps setMinute:00];
[timeZoneComps setSecond:01];
m_currentDate = [gregorian dateFromComponents:timeZoneComps];
When the user wants to go next month, I highlight the first date of that month. So, in this case, the date will be 1-06-2014,00:00:01.
Here is the code:
- (void)showNextMonth
{
// Move the date context to the next month
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *dateComps = [[NSDateComponents alloc] init];
[dateComps setMonth:1];
m_currentMonthContext =[gregorian dateByAddingComponents:dateComps toDate:m_currentMonthContext options:0];
NSDateComponents *weekdayComponents1 = [gregorian components:(NSDayCalendarUnit | NSWeekdayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit) fromDate:m_currentMonthContext];
NSInteger nextMonth = [weekdayComponents1 month];
NSInteger nextyear = [weekdayComponents1 year];
NSDateComponents *weekdayComponents2 = [gregorian components:(NSDayCalendarUnit | NSWeekdayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit) fromDate:m_currentDate];
NSInteger currentDay = [weekdayComponents2 day];
NSInteger currentMonth = [weekdayComponents2 month];
NSInteger currentYear = [weekdayComponents2 year];
NSInteger selectedDay = 1;
if(nextMonth == currentMonth && nextyear == currentYear)
{
selectedDay = currentDay;
}
NSInteger month = nextMonth;
[gregorian setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
NSDateComponents *timeZoneComps=[[NSDateComponents alloc] init];
[timeZoneComps setDay:selectedDay];
[timeZoneComps setMonth:month];
[timeZoneComps setYear:nextyear];
[timeZoneComps setHour:00];
[timeZoneComps setMinute:00];
[timeZoneComps setSecond:01];
m_currentMonthContext =[gregorian dateFromComponents:timeZoneComps];
[self createCalendar];
}
When m_currentMonthContext is calculated on the second to last line of the above method, its value is 1-06-2014,00:00:01.
createCalendar implementation:
-(void)createCalendar
{
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *weekdayComponents = [gregorian components:(NSDayCalendarUnit | NSWeekdayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit)fromDate:m_currentMonthContext];
NSInteger month = [weekdayComponents month];
NSInteger year = [weekdayComponents year];
}
Here I get month as 5 and year as 2014, but the date is 1-06-2014. This happens only in US time zone, in all other time zones it is working fine.
So I want to know how to handle timezones effectively, or in other sense, how to make sure that NSDate does not change even if time zone changes.
The proximate cause is that the time zone is not consistently set on the calendar when calculating dates and date components. Sometimes you set the time zone to UTC, and sometimes not, which is going to cause inconsistencies, as sometimes offsets for local time will be applied, and sometimes not.
In detail, in your situation, m_currentMonthContext is an NSDate which represents the UTC time one second after midnight on June 1st, 2014. In your createCalendar method, you create a calendar that is the local time of the user, and calculate the components for such a date. In all time zones in the US, it is still the month of May one second after midnight on June 1st, 2014 UTC. An example in code, that can be run in isolation:
NSCalendar *utcCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
[utcCalendar setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"UTC"]];
NSCalendar *localCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *june = [NSDate dateWithTimeIntervalSince1970:1401580801];
NSDateComponents *utcComponents = [utcCalendar components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:june];
NSDateComponents *localComponents = [localCalendar components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:june];
NSLog(#"utc : %#", utcComponents);
NSLog(#"local: %#", localComponents);
Here in MDT time zone, this logs:
utc :
Calendar Year: 2014
Month: 6
Leap month: no
Day: 1
local:
Calendar Year: 2014
Month: 5
Leap month: no
Day: 31
To recap, you're keeping a date in memory that's been calculated to represent a certain calendar date in UTC time, and then calculating the calendar date in the user's local time, but it seems you have an incorrect expectation that calendars for different time zones will interpret the same date the same way.
So, what to do? Your example is pretty complex, but it seems there's no need at all to store date components sometimes in UTC time zone and sometimes not - be consistent. Now, it also seems to me that you can be much much simpler in your code if you just want to find the first day of the next month.:
NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *comps = [cal components:(NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit) fromDate:[NSDate date]];
[comps setMonth:[comps month] + 1];
[comps setDay:1];
I tested this with December 15th, 2014, and it worked to create January 1st, 2015 in my local time. Hopefully that is consistent behavior.
To sum up - it's very likely a bug to not use a consistent calendar for your date component calculations. Sometimes having UTC and sometimes local is going to cause you nightmares. It seems like you should always calculate in local time, but I don't know the whole context of your application so can't make a blanket statement for that. Also, it should be safe to not rely on incessant conversions between dates and date components, and instead have the date component be your source of truth. That is, I mean it seems convoluted to convert date components to dates always to store in instance variables, but then to immediately convert the dates back into date components every time they're used - it seems better to just work with date components as much as possible.
From the comment, I hope I understand your question correctly. You can try this code:-
NSDate * nowDate = [NSDate date];
NSLog(#"nowDate: %#",nowDate);
NSDateFormatter *df = [NSDateFormatter new];
[df setDateFormat:#"dd/MM/yyyy HH:mm"];
df.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:[NSTimeZone localTimeZone].secondsFromGMT];
NSString *localDate = [df stringFromDate:nowDate];
NSLog(#"localDate: %#", localDate);
Output:
2014-05-24 23:03:06.205 TestTimeZone[10214:60b] nowDate: 2014-05-24
15:03:06 +0000
2014-05-24 23:03:06.209 TestTimeZone[10214:60b] localDate: 24/05/2014
23:03
[NSDate date] always return GMT+0 date, no matter where is your timezone. May be just use this? At the same time I used NSDateFormatter to set to my local date based on my laptop. You can try to change to a few different timezones on your mac while running the above code on simulator. [NSDate date] might be just what you need.
If I have a string representing a time, say "10:45 am", and do the following to parse the string:
NSDateFormatter *dateFormat;
dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"h:mm a"];
NSLog(#"%#", [dateFormat dateFromString:#"10:45 AM"]);
I would get this logged:
2013-09-09 17:52:30.416 TimeTest[49491:a0b] 2000-01-01 15:45:00 +0000
How can I create an NSDate for the current day at the given time? I tried this
NSDate *date = [NSDate date];
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:#"h:mm a"];
NSDate *time = [formatter dateFromString:#"10:45 AM"];
NSDateComponents *timeComponents = [[NSCalendar currentCalendar] components:(NSHourCalendarUnit | NSMinuteCalendarUnit ) fromDate:time];
NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date];
NSDateComponents *newComponents = [[NSDateComponents alloc]init];
newComponents.timeZone = [NSTimeZone systemTimeZone];
[newComponents setDay:[dateComponents year]];
[newComponents setMonth:[dateComponents month]];
[newComponents setYear:[dateComponents year]];
[newComponents setHour:[timeComponents hour]];
[newComponents setMinute:[timeComponents minute]];
NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *combinedDate = [gregorianCalendar dateFromComponents:newComponents];
NSLog(#"%#", combinedDate);
with the result
2013-09-09 19:57:14.506 TimeTest[49712:a0b] 2019-03-06 15:45:00 +0000
How should I go about this?
I'm not exactly sure what you are looking for. For what I understand, you want to build a date with the current year, month and day, but with your supplied time by parsing it from a string.
If that is the case, as others have pointed out, you need to play with NSDateComponents.
Based on your code I wrote these lines. They should build a date by merging two dates. The current one and the one you parsed.
// Get the full current date
NSDate *date = [NSDate date];
// Get the current calendar
NSCalendar *calendar = [NSCalendar currentCalendar];
// Split the date into components but only take the year, month and day and leave the rest behind
NSDateComponents *dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date];
// Build the date formatter
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:#"h:mm a"];
// Convert the string time into an NSDate
NSDate *time = [formatter dateFromString:#"10:45 AM"];
// Split this one in components as well but take the time part this time
NSDateComponents *timeComponents = [[NSCalendar currentCalendar] components:(NSHourCalendarUnit | NSMinuteCalendarUnit ) fromDate:time];
// Do some merging between the two date components
dateComponents.hour = timeComponents.hour;
dateComponents.minute = timeComponents.minute;
// Extract the NSDate object again
NSDate *result = [calendar dateFromComponents:dateComponents];
// Check if this was what you where looking for
NSLog(#"%#",result);
Please be aware that this sample code is by far non-optimized. There are more crisp ways to obtain what you are looking for by using time intervals, but I felt like you wanted a dirty simple example on how to do components copy and paste and then extracting dates.
This will create a date for the beginning of the day in the current time zone.
NSDate *today = [NSDate date];
NSTimeInterval interval;
NSCalendar *cal = [NSCalendar currentCalendar];
[cal rangeOfUnit:NSDayCalendarUnit
startDate:&today
interval:&interval
forDate:today];
Now we add the time:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
// I have to set the locale to posix_en_us, as my system is using 24hour style as default
dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
[dateFormatter setDateFormat:#"hh:mm a"];
NSDate *time = [dateFormatter dateFromString:#"10:45 AM"];
NSDateComponents *comps = [cal components:(NSHourCalendarUnit | NSMinuteCalendarUnit)
fromDate:time];
NSDate *dateAndTime = [cal dateByAddingComponents:comps
toDate:today
options:0];
dateAndTime will now be todays date with 10:45 am in the local timezone.
controlling in the debugger:
po dateAndTime
$0 = 0x41b7df138c00000d 2013-09-10 08:45:00 +0000
This is correct, as my timezone is 2 hours ahead to GMT, as we still have summer time.