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];
Related
I am working on a project where i need to set an alarm on 7 days before particular date the user has selected from date picker.
I used the following code to get the date from user
NSDateFormatter *df = [[NSDateFormatter alloc]init];
[df setDateStyle:NSDateFormatterFullStyle];
NSString *dateStr = [NSString stringWithFormat:#"%#",[df stringFromDate:datePickerObj.date]];
[df release];
Can any one please tell me how to get the date of 7 days previous to the selected date.
Thanks in advance
Use dateByAddingComponents:toDate:options:, like this:
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [[NSDateComponents alloc] init];
components.day = -7;
NSDate *earlierDate = [calendar dateByAddingComponents:components
toDate:datePickerObj.date options:0];
hi i have 2 dates in string format
base_date_string = 10-12-01 12:00:00
current_date_string = 10-12-23 10:18:00
both the above values are in string
i want to get the number of days elapsed between these 2 dates
I tried to convert them to NSDate using NSDateFormatters and then getting the difference.
I realised that string does not properly converts to NSDate
when i convert to nsdate i got
base_date:::2010-12-01 06:30:00 +0000
current_date::::2010-12-23 04:48:19 +0000 (the time portion is not perfect)
Formatter class that i used is:
NSDateFormatter *formatter1 = [[NSDateFormatter alloc] init];
[formatter1 setDateFormat:#"yy-MM-dd HH:mm:ss"];
NSDate *base_date = [formatter1 dateFromString:#"10-12-01 12:00:00"];
[formatter1 release];
NSDateFormatter *formatter2 = [[NSDateFormatter alloc] init];
[formatter2 setDateFormat:#"yy-MM-dd HH:mm:ss"];
NSDate *current_date = [formatter2 dateFromString:current_date_string];
[formatter2 release];
//subrtrcation of basedate from current date to get elapsed number of days
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *diff = [calendar components:(NSDayCalendarUnit)
fromDate:base_date toDate:current_date options:0];
int date_value = [diff day];
Please any help is appreciated
30 seconds in the NSDate documentation revealed:
-[NSDate timeIntervalSinceDate:]
So using the dates in your question...
NSTimeInterval difference = [current_date timeIntervalSinceDate:base_date];
difference = fabs(difference);
NSLog(#"there are %f seconds between %# and %#", difference, current_date, base_date);
edit
ok, so the problem is not date differencing. You're observing that the string you're inputting is 5 and 1/2 hours ahead of the date you're getting back.
Well, let's look at this. The date returned is in GMT time (as denoted by the +0000). 5 and 1/2 hours ahead of that is the timezone used in India. So. Are you in India? If you are, then this is just a matter of needing to -setTimezone: on your NSDateFormatter.
You can use this code of function to get the difference between 2 dates
-(int)howManyDaysHavePast:(NSDate*)lastDate :(NSDate*)today {
NSDate *startDate = lastDate;
NSDate *endDate = today;
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
unsigned int unitFlags = NSDayCalendarUnit;
NSDateComponents *components = [gregorian components:unitFlags
fromDate:startDate
toDate:endDate options:0];
[gregorian release];
int days = [components day];
return days;
}
hAPPY iCODING...
Use the following code
NSDateFormatter *formatter1 = [[NSDateFormatter alloc] init];
[formatter1 setDateFormat:#"yy-MM-dd HH:mm:ss"];
NSDate *base_date = [formatter1 dateFromString:#"10-12-01 12:00:00"];
NSDate *current_date = [formatter2 dateFromString:current_date_string];
[formatter1 release];
NSTimeInterval difference = [current_date timeIntervalSinceDate:base_date];
Then you will get difference in number of seconds. Then you can get in number of days as following
float days = difference/86400;
The "days" consists the number of days that the current_date is differ from the base_date.
I have a date in UILabel(like 'Dec 14, 2010). This date i want to set as minimum date of my UIDatepicker. How can i do this please reply?
Thanks
Nishant
Convert your UILabel text in to date format using NSDateFormatter and put that value replacing "Date" in following example:
UIDatepicker *datePicker;
NSDate *Date=[NSDate date];
datePicker.minimumDate=Date;
You can use NSDateFormatter and use setDateFormat method for setting Date format.
[formatter setDateFormat:#"MMM dd,yyyy"];
NSDate *date = [formatter dateFromString:lblDate.text];
datePicker.minimumDate=date;
NSCalendar *calendar = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *currentDate = [NSDate date];
NSDateComponents *comps = [[[NSDateComponents alloc] init] autorelease];
[comps setYear:0];
NSDate *maxDate = [calendar dateByAddingComponents:comps toDate:currentDate options:0];
[comps setYear:-5];
NSDate *minDate = [calendar dateByAddingComponents:comps toDate:currentDate options:0];
[datePicker setMaximumDate:maxDate];
[datePicker setMinimumDate:minDate];
it showing five year date.......
See the minimum time from the current date to one month:
NSDate* currentTime = [NSDate date];
[datePicker setMinimumDate:[currentTime dateByAddingTimeInterval:43200]];//min time +12:00 for the current date
[datePicker setMaximumDate:[currentTime dateByAddingTimeInterval:2592000]]; // max day (+ 30 )
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.
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.