A seemingly simple question...how can I return a list of days for any specified month?
NSDate *today = [NSDate date]; //Get a date object for today's date
NSCalendar *c = [NSCalendar currentCalendar];
NSRange days = [c rangeOfUnit:NSDayCalendarUnit
inUnit:NSMonthCalendarUnit
forDate:today];
I basically want to use that, but replace today with say, the month of January, so I can return all of those days
Carl's answer works on Mac. The following works on Mac or iPhone (no dateWithNaturalLanguageString: available there).
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
// Set your year and month here
[components setYear:2015];
[components setMonth:1];
NSDate *date = [calendar dateFromComponents:components];
NSRange range = [calendar rangeOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitMonth forDate:date];
NSLog(#"%d", (int)range.length);
You can make your date with pretty much any string:
NSDate *date = [NSDate dateWithNaturalLanguageString:#"January"];
Then the rest of your code will work as-is to give you back the NSRange for the number of days in January.
Related
i have an array of NSManagedObject take from my core data, and i want filter the array with the date that is >= of today, so i do this:
NSPredicate *pred = [NSPredicate predicateWithFormat:#"(firstAired >= %#)", [NSDate date]];
but find me only the date > of today, and the date of today don't, why?
You should create Midnight date,like this, and pass it to the predicate
NSDateComponents *currentComponents = [[NSCalendar currentCalendar]components:NSMinuteCalendarUnit|NSHourCalendarUnit|NSSecondCalendarUnit fromDate:[NSDate date]];
[currentComponents setMinute:0];
[currentComponents setHour:0];
[currentComponents setSecond:0];
NSCalendar *calendar = [[NSCalendar alloc]initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *dateToCheck = [calendar dateFromComponents:currentComponents];
NSDate *now = [NSDate date];
NSCalendar *calendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
calendar.timeZone = [NSTimeZone timeZoneWithAbbreviation:#"GMT"];
NSDateComponents *components = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:now];
[components setHour:00];
NSDate *today = [calendar dateFromComponents:components];
in this way works, thanks to all...
[NSDate date] is the current time. So this predicate will fetch only records where firstAired is later today or later, and not earlier today. Construct an NSDate with the time 00:00:00.
Because [NSDate date] returns the exact date with hour, minute, second .... of the instant when it is executed. If you want to search for every "today" item then you have to change [NSDate date] with a NSDate object for today at midnight. That is, extract the date components from NSDate.date and then, using the components year, month and day build a new date object with hour: 00:00AM.
Is there a way to subtract the current date by 5. say if today is 2008-12-9 i need to get the date 5 days back. If we output this, the date should display as 2008-12-4.
How can i code this programatically? or a tutorial that would help
Always use NSCalendar and NSDateComponents for date calculations. This will take into account oddities like leap years with 29 days in February, leap seconds and daylight saving changes.
NSDate *date = [NSDate date]; // Using current date here
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [[NSDateComponents alloc] init];
components.day = - 5; // Find date for 5 days ago
NSDate *newDate = [calendar dateByAddingComponents:components toDate:date options:0];
Use NSDateComponents
NSDate *today = [NSDate date];
NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDateComponents *offsetComponents = [[[NSDateComponents alloc] init] autorelease];
[offsetComponents setDays:-5];
NSDate *fiveDaysAgo = [gregorian dateByAddingComponents:offsetComponents toDate:today options:0];
to convert it to a string with the preferred format, use NSDateFormatter
NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
[dateFormatter setDateFormat:#"yyyy-MM-dd"];
NSString *formattedDateString = [dateFormatter stringFromDate:fiveDaysAgo];
This is the brute-force way:
Sustract 5 from DAY.
If DAY < 0, add number of days of the previous month and sustract 1 from MONTH.
If MONTH < 0, add number of month of a year and sustract 1 from YEAR.
The advantage of the brute-force approach is that it will work with every language.
#define SOME_HOUR -24*5
NSDate *today = [NSDate date];
NSDate *someDay = [NSDate dateWithTimeInterval:60*60*SOME_HOUR sinceDate:today];
I have a class that holds an start date and an end date, normally initialised to the firt and last second of the month.
The following function works correctly going from Nov 2010 forwards into December and back again however going backwards from November ends up with startDate set to
2010-09-30 23:00:00 GMT
Ie. a month and an hour ago.
Strangely the endDate is still correctly set to
2010-11-01 00:00:00 GMT
And going forward a month from this incorrect date also results in the correct time and date.
Is this a bug or am I doing something I shouldn't be ?
-(void) moveMonth:(NSInteger)byAmount { // Positive or negative number of months
NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
// Update the start date
[components setMonth:byAmount];
NSDate *newStartDate = [cal dateByAddingComponents:components toDate:[self startDate] options:0];
[self setStartDate:newStartDate];
// And the end date
[components setMonth:1];
NSDate *newEndDate = [cal dateByAddingComponents:components toDate:[self startDate] options:0 ];
[self setEndDate:newEndDate];
}
SOLUTION: Answer correctly pointed out this is a DST issue
If you want to deal in absolute times and date then using the following avoids any DST being involved.
NSCalendar *cal = [[NSCalendar alloc ] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSTimeZone *zone = [NSTimeZone timeZoneWithName:#"GMT"];
[cal setTimeZone:zone];
It is probably not a bug but something related to DST changes in October-November period.
It would be easier to just grab the month and year of the current date, add/subtract the number of months difference, then generate a date from those new values. No need to worry about Daylight Saving changes, leap years, etc. Something like this ought to work:
-(void) moveMonth:(NSInteger)byAmount {
NSDate *now = [NSDate date];
NSCalendar *cal = [NSCalendar currentCalendar];
// we're just interested in the month and year components
NSDateComponents *nowComps = [cal components:(NSYearCalendarUnit|NSMonthCalendarUnit)
fromDate:now];
NSInteger month = [nowComps month];
NSInteger year = [nowComps year];
// now calculate the new month and year values
NSInteger newMonth = month + byAmount;
// deal with overflow/underflow
NSInteger newYear = year + newMonth / 12;
newMonth = newMonth % 12;
// month is 1-based, so if we've ended up with the 0th month,
// make it the 12th month of the previous year
if (newMonth == 0) {
newMonth = 12;
newYear = newYear - 1;
}
NSDateComponents *newStartDateComps = [[NSDateComponents alloc] init];
[newStartDateComps setYear: year];
[newStartDateComps setMonth: month];
[self setStartDate:[cal dateFromComponents:newDateComps]];
[newDateComps release];
// Calculate newEndDate in a similar fashion, calling setMinutes:59,
// setHour:23, setSeconds:59 on the NSDateComponents object if you
// want the last second of the day
}
Here is a way to do it properly. This method returns a new NSDate after adding/subtracting month "byAmount".
-(NSDate*) moveMonth:(NSInteger)byAmount {
NSDate *now = [NSDate date];
NSDateComponents *components = [[NSDateComponents alloc] init];
[components setMonth:byAmount];
NSDate *newDate = [[NSCalendar currentCalendar] dateByAddingComponents:components toDate:now options:0];
return newDate;
}
Can any one tell that how to find the date for the 3rd day from the current date iphone/ipad.
Thanks in advance
You can use this:
NSDate *today = [[NSDate alloc] init];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
[offsetComponents setDay:3];
NSDate *threeDaysFromToday = [gregorian dateByAddingComponents:offsetComponents toDate:today options:0];
Slightly modified example from Apple's own documentation on NSDate. Check the link out for further info and more examples.
Here is Sample Code
NSDate * currentDate=[NSDate date];
NSTimeInterval interval=[currentDate timeIntervalSince1970];
NSTimeInterval intervalForThirdDate=interval+86400*3;
NSDate *nextDate=[[NSDate alloc]initWithTimeIntervalSince1970:intervalForThirdDate];
NSDate *today = [NSDate date];
NSTimeInterval threeDays = 86400*3;
NSDate *threeDaysFromToday = [NSDate dateWithTimeInterval:threeDays sinceDate:today];
choose one:
NSDate *futureDate;
NSDateComponents *components = [[[NSDateComponents alloc] init] autorelease];
[components setDay:3];
futureDate = [[NSCalendar currentCalendar] dateByAddingComponents:components toDate:[NSDate date] options:0];
NSLog(#"%# - %#", [NSDate date], futureDate);
NSDate *futureDate = [[NSDate date] dateByAddingTimeInterval:3 * (24*60*60)];
[NSDate dateWithTimeIntervalSinceNow:86400*3]
But as someone mentioned above, DST might make this too inaccurate. Depends on how important that is.
Something like:
// get the gregorian calendar ready to go; use the getter for the current system
// calendar if you're happy to deal with other calendars too
NSCalendar *gregorianCalendar = [[NSCalendar alloc]
initWithCalendarIdentifier: NSGregorianCalendar];
// get an NSDate object that is three days in the future
NSDate *dateInFuture = [NSDate dateWithTimeIntervalSinceNow:3*24*60*60];
// grab the date components for the bits we want to print in this example
NSDateComponents *componentsOfDateInFuture =
[gregorianCalendar
components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit
fromDate:dateInFuture];
// and print
NSLog(#"in three days it'll be %04d/%02d/%02d",
componentsOfDateInFuture.year,
componentsOfDateInFuture.month,
componentsOfDateInFuture.day);
// clean up
[gregorianCalendar release];
EDIT: Pablo Santa Cruz's answer is better for ensuring you're three days in the future, given daylight savings concerns. This is how you'd decompose an NSDate to day/month/year though, for the purposes of having the date rather than simply an NSDate.
how can I calculate the calendar week? A year has 52/53 weeks and there are two rules:
-USA
-DIN 1355 / ISO 8601
I'd like to work with DIN 1355 / ISO 8601. How can I manage that?
Edit:
NSDate *today = [NSDate date];
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"ww"];
NSString *weeknumber = [dateFormat stringFromDate: today];
NSLog(#"week: %#", weeknumber);
Taken from http://iosdevelopertips.com/cocoa/date-formatter-examples.html
Where do I find the allowed date formats?
Use an NSCalendar and NSDateComponents.
NSCalendar *cal = [NSCalendar currentCalendar];
NSDateComponents *components = [cal components:NSWeekCalendarUnit fromDate:date];
NSInteger week = [components week];
Or use:
CFAbsoluteTime currentTime = CFAbsoluteTimeGetCurrent();
CFTimeZoneRef currentTimeZone = CFTimeZoneCopyDefault();
SInt32 weekNumber = CFAbsoluteTimeGetWeekOfYear(currentTime, currentTimeZone);
The numbering follows the ISO 8601 definition of week.
NSDate *today = [NSDate date];
NSCalendar *ISO8601 = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierISO8601];
ISO8601.firstWeekday = 2; // Sunday = 1, Saturday = 7
ISO8601.minimumDaysInFirstWeek = 4;
NSDateComponents *components = [ISO8601 components:NSCalendarUnitWeekOfYear fromDate:today];
NSUInteger weekOfYear = [components weekOfYear];
NSDate *mondaysDate = nil;
[ISO8601 rangeOfUnit:NSCalendarUnitYearForWeekOfYear startDate:&mondaysDate interval:NULL forDate:today];
NSLog(#"The current Weeknumber of Year %ld ", weekOfYear);
You should user NSDateFormatter like so:
NSDateFormatter *fm = [[NSDateFormatter alloc] initWithDateFormat:#"ww" allowNaturalLanguage:NO];
NSString *week = [fm stringFromDate: date];
There is many kinds of Canlendar.
Week number according to the ISO-8601 standard, weeks starting on Monday. The first week of the year is the week that contains that year's first Thursday (='First 4-day week'). The highest week number in a year is either 52 or 53. This year has 52 weeks.This is not the only week numbering system in the world, other systems use weeks starting on Sunday (US) or Saturday (Islamic).
More details: http://www.epochconverter.com/weeknumbers
And Apple does support that, so you could find correct way referred from https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSCalendar_Class/
For example, with ISO-8601 standard:
NSCalendar *ISO8601 = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierISO8601];
Hope this could help.