I found the codes to calculate days difference between two dates here.
I write a method :
-(NSInteger)daysWithinEraFromDate:(NSDate *) startDate toDate:(NSDate *) endDate
{
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
NSInteger startDay=[gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit: NSEraCalendarUnit forDate:startDate];
NSInteger endDay=[gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit: NSEraCalendarUnit forDate:endDate];
return endDay-startDay;
}
This method has a problem: it can't consider the timezone thing. Even I add a line like this:
[gregorian setTimeZone:[NSTimeZone localTimeZone]];
My test code is like this:
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSString *strDate = #"2012-09-03 23:00:00";
NSDate *dateStart = [dateFormat dateFromString:strDate];
strDate = #"2012-09-04 01:00:00";
NSDate *dateEnd = [dateFormat dateFromString:strDate];
NSLog(#"Days difference between %# and %# is: %d days",[dateFormat stringFromDate:dateStart],[dateFormat stringFromDate:dateEnd],[self daysWithinEraFromDate:dateStart toDate:dateEnd]);
The result is:
Days difference between 2012-09-03 23:00:00 and 2012-09-04 01:00:00 is: 0 days
I want to get 1 day as result by the number of midnights between the two dates. My timezone is GMT +8. But this calculation is based on GMT, so I get the wrong days number. Is there anyway to solve this problem? Thank you.
Scott Lemmon's method can solve my problem. I rewrite my code like this:
-(NSInteger)daysWithinEraFromDate:(NSDate *) startDate toDate:(NSDate *) endDate
{
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
[gregorian setTimeZone:[NSTimeZone localTimeZone]];
NSDate *newDate1 = [startDate dateByAddingTimeInterval:[[NSTimeZone localTimeZone] secondsFromGMT]];
NSDate *newDate2 = [endDate dateByAddingTimeInterval:[[NSTimeZone localTimeZone] secondsFromGMT]];
NSInteger startDay=[gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit: NSEraCalendarUnit forDate:newDate1];
NSInteger endDay=[gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit: NSEraCalendarUnit forDate:newDate2];
return endDay-startDay;
}
If the time zone offset isn't working, how about just add or subtract it manually instead?
In your case NSDate *newDate = [oldDate dateByAddingTimeInterval:(-8 * 60 * 60)]; to subtract off your +8 hours.
Or if you want to find the GMT offset automatically as well then it would simply be NSDate *newDate = [oldDate dateByAddingTimeInterval:(-[[NSTimeZone localTimeZone] secondsFromGMT])
Another thought:
A perhaps easier solution would be to just disregard the time information altogether. Just set it to the same arbitrary number for both dates, then as long as the dates come from the same timezone you will always get the correct number of mid-nights between them, regardless of GMT offset.
What you really want is the NSDate method timeIntervalSinceDate:, and take that result and if it's more than 0 but less than 86400 (the number of seconds in a day), that's one day. Otherwise, divide your result by 86400 and you'll get the number of days.
The way you currently have your code, there's only 2 hours between the two days and that's why you are seeing a result of 0 and not one.
Edit - and to determine if midnight has happened, let's try this function I just wrote off the top of my head:
- (NSDate *) getMidnightDateFromDate: (NSDate *) originalDate
{
NSDateComponents *components = [[NSCalendar currentCalendar] components:NSIntegerMax fromDate:originalDate];
[components setHour:0];
[components setMinute:0];
[components setSecond:0];
NSDate *midnight = [[NSCalendar currentCalendar] dateFromComponents:components];
return(midnight);
}
- (BOOL) howManyDaysDifferenceBetween: startDate and: endDate
{
NSDate * firstMidnight = [self getMidnightDateFromDate: startDate];
NSDate * secondMidnight = [self getMidnightDateFromDate: endDate];
NSTimeInterval timeBetween = [firstMidnight timeIntervalSinceDate: secondMidnight];
NSInteger numberOfDays = (timeBetween / 86400);
return(numberOfDays);
}
which I'm basing off Dave Delong's answer to this question. No guarantees that my code will work (I didn't test it), but I think the concept is sound.
Related
I have a very interesting problem: When calculating the number of days between two dates, my calculator gives the wrong results for the month of March only. I have two text fields, one for each date. If I enter 3/7/12 in date1, and 3/13/12 in date2, the result is 7, which is correct (I am counting the first day as well). But when I enter date1 = 3/7/12 and date2 = 3/14/12, the result is still 7, but it should be 8. Likewise, if I enter date1 = 3/7/12 and date2 = 3/23/12, the result should be 17, but it is 16. If I change the month to April so that date1 = 4/7/12 and date2 = 4/23/12, the result is 17. Every month is working as intended, only the month of March is giving me wrong results. Does anyone have any idea what I am missing? Is this a timezone problem? How do I fix it? Here is my code:
NSDateFormatter *dateFormatter1 = [[NSDateFormatter alloc] init];
[dateFormatter1 setDateFormat:#"MM/dd/yyyy"];
NSDate *startdate1 = [dateFormatter1 dateFromString: date1.text];
NSDateFormatter *dateFormatter2 = [[NSDateFormatter alloc] init];
[dateFormatter2 setDateFormat:#"MM/dd/yyyy"];
NSDate *enddate2 = [dateFormatter2 dateFromString: date2.text];
int start1 = [startdate1 timeIntervalSince1970];
int end2 = [enddate2 timeIntervalSince1970];
double difference12 = end2-start1;
int days12;
days12 =(int)((double)difference12/(3600.0*24.00)+1);
result12.text = [[NSString alloc] initWithFormat:#"%i", days12]
If you use NSCalendar, you won't need to deal with Daylight Savings Time calculation.
int days = [[[NSCalendar currentCalendar] components:NSDayCalendarUnit
fromDate:startDate1
toDate:endDate2
options:0] day] + 1;
Most like this is a daylight savings issue (March 11th, 2012). Set the date formatters' timezones to:
[NSTimeZone timeZoneForSecondsFromGMT:0];
This should fix the issue.
To add to others, please do not rely on number of seconds in a day being 86400 all the time, it won't. Be sure to watch Session 211 Performing Calendar Calculations from WWDC 2011.
You can think of NSDate as a point in time. If you want to calculate number of days between two dates, this is a calendar issue and there are more than one calendars (like the Mayan calendar).
What you need is NSDateComponents:
NSDate *dateToday = [NSDate date];
NSDateComponents *dateBComponent = [[NSDateComponents alloc] init];
[dateBComponent setDay:-10];
NSDate *date10DaysAgo = [[NSCalendar currentCalendar] dateByAddingComponents:dateBComponent
toDate:dateToday
options:0];
NSCalendar *calendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDateComponents *components = [calendar components:NSDayCalendarUnit
fromDate:date10DaysAgo
toDate:dateToday
options:0];
NSLog(#"Difference: %d", components.day);
I am using the following NSCalendar method to get the number of days in a calendar year:
NSRange range = [gregorian rangeOfUnit:NSDayCalendarUnit
inUnit:NSYearCalendarUnit
forDate:date];
I am expecting a range.length return value of type NSRange which is 365 or 366 (days).
However, this code returns a range.length of 31 for a date value of 2005-06-06.
What is wrong with my code?
This is the full code snippet:
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
[subArray enumerateObjectsUsingBlock:
^(NSDate *date, NSUInteger idx, BOOL *stop) {
NSUInteger numberOfDays = [gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit:NSYearCalendarUnit forDate:date];
}];
This calculates the number of days of a year of a given date:
NSDate *someDate = [NSDate date];
NSDate *beginningOfYear;
NSTimeInterval lengthOfYear;
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
[gregorian rangeOfUnit:NSYearCalendarUnit
startDate:&beginningOfYear
interval:&lengthOfYear
forDate:someDate];
NSDate *nextYear = [beginningOfYear dateByAddingTimeInterval:lengthOfYear];
NSInteger startDay = [gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit:NSEraCalendarUnit
forDate:beginningOfYear];
NSInteger endDay = [gregorian ordinalityOfUnit:NSDayCalendarUnit
inUnit:NSEraCalendarUnit
forDate:nextYear];
NSInteger daysInYear = endDay - startDay;
Sad caveat: This does not work correctly for year 1582.
The year 1582, the year when Gregor introduced the currently widespread used calendar, needed a fix to align solar with calendar years. So they went with the pragmatic solution: They just dropped October 5-14. (They were not crazy enough to change weekdays, too). As a result the year 1582 only has 355 days.
Addendum: The code above only works correctly for years after 1582. It returns 365 days for the year 1500, for example, even though this year was a leap year in the then used julian calendar. The gregorian calendar starts at October 15, 1582. Computations made on the gregorian calendar are just not defined before that date. So in this way Apple's implementation is correct. I'm not aware of a correct implementation for years before 1583 on Cocoa.
Here's a relatively clean version. It's a category on NSCalendar.
- (NSInteger) daysInYear:(NSInteger) year {
NSDateComponents *dateComponents = [[NSDateComponents alloc] init];
dateComponents.year = year;
dateComponents.month = dateComponents.day = 1;
NSDate *firstOfYear = [self dateFromComponents:dateComponents];
dateComponents.year = year + 1;
NSDate *firstOfFollowingYear = [self dateFromComponents:dateComponents];
return [[self components:NSDayCalendarUnit
fromDate:firstOfYear
toDate:firstOfFollowingYear
options:0] day];
}
Thanks to AKV for pointing out that -components:fromDate:toDate:options will work in this case.
This doesn't seem to work for 1582 or prior, which per Nikolai Ruhe's answer is because Gregorian calendar calculations simply aren't defined prior to then.
What about finding number of days in a given year as: Although this is not the relative solution for the question.
-(NSInteger)daysBetweenTwoDates:(NSDate *)fromDateTime andDate:(NSDate *)toDateTime{
NSDate *fromDate;
NSDate *toDate;
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar rangeOfUnit:NSDayCalendarUnit startDate:&fromDate interval:NULL forDate:fromDateTime];
[calendar rangeOfUnit:NSDayCalendarUnit startDate:&toDate interval:NULL forDate:toDateTime];
NSDateComponents *difference = [calendar components:NSDayCalendarUnit fromDate:fromDate toDate:toDate options:0];
return [difference day];
}
-(void)someMethod {
NSString *yourYear=#"2012";
NSDate *date1 = [NSDate dateWithString:[NSString stringWithFormat:#"%#-01-01 00:00:00 +0000",yourYear]];
NSDate *date2 = [NSDate dateWithString:[NSString stringWithFormat:#"%#-12-31 00:00:00 +0000",yourYear]];
NSInteger numberOfDays=[self daysBetweenTwoDates:date1 andDate:date2];
NSLog(#"There are %ld days in between the two dates.", numberOfDays);
}
Edit:
As dateWithString: is deprecated, you can use
NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init];
[dateFormatter dateFormat]=#"dd-MM-yyyy";
NSDate *date=[dateFormatter dateFromString:dateString];
to form date1 and date2
You are getting the number of days in the month of your date.
You could use the same function and just pass in a date with February as the month. If range.length returns 28, the Total days in the year will be 365, if it returns 29, then the number of days will be 366.
I'm trying get only the Saturdays and Sundays between two dates, but I don't know why get me free days on a week.
Here is my code:
- (BOOL)checkForWeekend:(NSDate *)aDate {
BOOL isWeekendDate = NO;
NSCalendar *calendar = [NSCalendar currentCalendar];
NSRange weekdayRange = [calendar maximumRangeOfUnit:NSWeekdayCalendarUnit];
NSDateComponents *components = [calendar components:NSWeekdayCalendarUnit fromDate:aDate];
NSUInteger weekdayOfDate = [components weekday];
if (weekdayOfDate == weekdayRange.location || weekdayOfDate == weekdayRange.length) {
// The date falls somewhere on the first or last days of the week.
isWeekendDate = YES;
}
return isWeekendDate;
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
NSString *strDateIni = [NSString stringWithString:#"28-01-2012"];
NSString *strDateEnd = [NSString stringWithString:#"31-01-2012"];
NSDateFormatter *df = [[NSDateFormatter alloc] init];
[df setDateFormat:#"dd-MM-yyyy"];
NSDate *startDate = [df dateFromString:strDateIni];
NSDate *endDate = [df dateFromString:strDateEnd];
unsigned int unitFlags = NSMonthCalendarUnit | NSDayCalendarUnit;
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *comps = [gregorian components:unitFlags fromDate:startDate toDate:endDate options:0];
// int months = [comps month];
int days = [comps day];
for (int i=0; i<days; i++)
{
NSTimeInterval interval = i;
NSDate * futureDate = [startDate dateByAddingTimeInterval:interval];
BOOL isWeekend = [self checkForWeekend:futureDate]; // Any date can be passed here.
if (isWeekend) {
NSLog(#"Weekend date! Yay!");
}
else
{
NSLog(#"Not is Weekend");
}
}
}
The problem:
The issue was caused by NSTimeInterval interval = i; The logic of the for loop was to iterate by days. Setting the time interval to i was iterating by seconds.
From documentation on NSTimeInterval
NSTimeInterval is always specified in seconds;
The answer:
Changing the NSTimeInterval line to
NSTimeInterval interval = i*24*60*60;
Here is a link to another answer I posted on SO (shameless, I know). It has some code that may help you with dates in the future. The methods are implemented as categories of NSDate, meaning they become methods of NSDate.
There are several functions there that help with weekends. But these two might be most helpful:
- (NSDate*) theFollowingWeekend;
- (NSDate *) thePreviousWeekend;
They return the date of the weekend following and prior to the receiver (self).
Generally, you should not use the notion that a day is 86400 seconds, and should use NSDateComponents and NSCalendar. This works even when daylight savings time transitions occur between dates. Like this:
- (NSDate *) dateByAddingDays:(NSInteger) numberOfDays {
NSDateComponents *dayComponent = [[NSDateComponents alloc] init];
dayComponent.day = numberOfDays;
NSCalendar *theCalendar = [NSCalendar currentCalendar];
return [theCalendar dateByAddingComponents:dayComponent toDate:self options:0];
}
One very important thing to remember is that one day is not (necessarily) equal to 24*60*60 seconds. And you should not do date arithmetic yourself
What you really need to do might seem a little tedious but this is the correct thing to do: use NSCalendar and – dateByAddingComponents:toDate:options:
See Calendrical Calculations guide.
I want to set the NSDate time with my desired hours:minutes:seconds
currently im working with NSDate component but it is not giving the desired result
[comps setHour: -hours];
[comps setMinute:0];
[comps setSecond:0];
NSDate *minDate = [calendar_c dateFromComponents:comps];
This works great as an NSDate category.
/** Returns a new NSDate object with the time set to the indicated hour,
* minute, and second.
* #param hour The hour to use in the new date.
* #param minute The number of minutes to use in the new date.
* #param second The number of seconds to use in the new date.
*/
-(NSDate *) dateWithHour:(NSInteger)hour
minute:(NSInteger)minute
second:(NSInteger)second
{
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components: NSYearCalendarUnit|
NSMonthCalendarUnit|
NSDayCalendarUnit
fromDate:self];
[components setHour:hour];
[components setMinute:minute];
[components setSecond:second];
NSDate *newDate = [calendar dateFromComponents:components];
return newDate;
}
With the above category, if you have an existing date you want to change the time on, you do so like this:
NSDate *newDate = [someDate dateWithHour:10 minute:30 second:00];
If, however, you are trying to add or subtract hours from an existing date, a category method to do that is also straightforward:
/** Returns a new date with the given number of hours added or subtracted.
* #param hours The number of hours to add or subtract from the date.
*/
-(NSDate*)dateByAddingHours:(NSInteger)hours
{
NSDateComponents *components = [[NSDateComponents alloc] init];
[components setHour:hours];
return [[NSCalendar currentCalendar]
dateByAddingComponents:components toDate:self options:0];
}
Your approach should work fine. I needed a solution for this type problem (setting the individual date components) and the following code works as expected for me. My situation: I wanted to create a date object that used the current date but had the time set to a value that was passed in as a string.
NSString *string = #"7:00";
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
NSDateFormatter *timeOnlyFormatter = [[NSDateFormatter alloc] init];
[timeOnlyFormatter setLocale:locale];
[timeOnlyFormatter setDateFormat:#"h:mm"];
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *today = [NSDate date];
NSDateComponents *todayComps = [calendar components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) fromDate:today];
NSDateComponents *comps = [calendar components:(NSHourCalendarUnit | NSMinuteCalendarUnit) fromDate:[timeOnlyFormatter dateFromString:string]];
comps.day = todayComps.day;
comps.month = todayComps.month;
comps.year = todayComps.year;
NSDate *date = [calendar dateFromComponents:comps];
[calendar release];
[timeOnlyFormatter release];
[locale release];
One thing to note is that you really have to pay attention to time zones when you are judging whether a time appears to be accurate. For example, in my app, when you stop at a breakpoint, you will see the time in GMT (so it looks different than the input time, which is in my local time), but when the time is actually displayed on screen in the app, it is being formatted to display in the local timezone. You may need to take this into consideration to determine whether the result is actually different from what you would expect.
If this does not help, can you elaborate on "not giving the desired result"? What result is it giving and how does that compare to what you expected?
is Swift2
extension NSDate {
func dateWithHour (hour: Int, minute:Int, second:Int) ->NSDate?{
let calendar = NSCalendar.currentCalendar(),
components = calendar.components([.Day,.Month,.Year], fromDate: self)
components.hour = hour;
components.minute = minute;
components.second = second;
return calendar.dateFromComponents(components)
}
}
You can set 0 to hour, min, and second.
NSDateFormatter *tFmt = [[NSDateFormatter alloc] init];
tFmt.dateFormat = #"yyyy-MM-dd";
NSString *strNowDate = [NSString stringWithFormat:#"%# 00:00:00",[tFmt stringFromDate:[NSDate date]]];
NSDate *nowDate = [NSDate dateWithString:strNowDate formatString:#"yyyy-MM-dd HH:mm:ss"];
Swift 5 solution (based on #dattk answer) for those who fear Deprecation warnings :)
func date(withHour hour: Int, withMinute minute: Int, withSeconds second: Int) -> Date? {
let now = Date()
let calendar = NSCalendar.current
var components = calendar.dateComponents([.day,.month,.year], from: now)
components.hour = hour
components.minute = minute
components.second = second
return calendar.date(from: components)
}
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *comps = [calendar components:(NSCalendarUnitHour | NSCalendarUnitMinute) fromDate:[NSDate date]];
comps.hour = 0;
comps.minute = 15;
NSDate *date = [calendar dateFromComponents:comps];
iOS 8
I would like to work out the difference in months
at the moment I have this code:
dateInterval = [endDate timeIntervalSinceDate:startDate];
But that returns a value in seconds, I would like to see the difference between the dates in months.
How would I do this?
Thanks
NSDateFormatter *inputFormatter = [[NSDateFormatter alloc] init];
[inputFormatter setDateFormat:#"dd/MM/yyyy"];
NSDate *startDate = [inputFormatter dateFromString:#"07/03/2011"];
NSDate *endDate = [inputFormatter dateFromString:#"07/06/2011"];
NSInteger month_delta = [[[NSCalendar currentCalendar] components: NSMonthCalendarUnit fromDate: startDate toDate: endDate options: 0] month];
NSLog(#"---------------------------->>%d", month_delta);
[inputFormatter release]; // <-- in case not using ARC
it will log:
---------------------------->>3
You can create a NSDateComponents from the NSDates in question and just subtract the total months. (Total months = 12*year+currentMonth)
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSDateComponents_Class/Reference/Reference.html#//apple_ref/occ/cl/NSDateComponents