I am trying to calculate an interval between now and a user defined date in days so that the results appear in a label on tapping a button.
The difference is always -4080 I am not sure what is wrong with my equation.
Thank you for your help
- (void)LabelChange2:(id)sender{
NSDateFormatter *df3 = [[NSDateFormatter alloc] init];
df3.dateStyle = NSDateFormatterMediumStyle;
labelDOB.text = [NSString stringWithFormat:#"%#",
[df3 stringFromDate:datepick.date]];
}
NSDate * df3 = [datePick date];
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *comps = [gregorian components: NSDayCalendarUnit
fromDate: [NSDate date]
toDate: df3
options: 0];
int days = [comps day];
labelResult.text = [NSString stringWithFormat:#"%i", days];
Your code works fine. However if I run the code with the datePick pointer set to nil I will get an answer of -4080 from this code. You should check your connections to the UIDatePicker.
Related
quick question I used the following code to retrieve a difference between two timestamps.
The minutes are given to me now in 0.5 hrs.
how do I get that into minutes (NSInteger format)?
NSDateFormatter* dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
[dateFormatter setLocale:[[[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"] autorelease]];
[dateFormatter setDateFormat:#"mm:ss"];
NSDate* firstDate = [dateFormatter dateFromString:#"06:00"];
NSDate* secondDate = [dateFormatter dateFromString:#"17:30"];
NSTimeInterval timeDifference = [secondDate timeIntervalSinceDate:firstDate];
I'm using an NSInteger to get the full hours, but can't figure out the minutes... must be too late at night for me :-/
NSInteger hoursBetweenDates = timeDifference / 60;
NSInteger minutesBetweenDates = ??;
NSLog(#"RAW: %f", timeDifference);
NSLog(#"Hours: %i", hoursBetweenDates);
NSLog(#"Minutes: %i", minutesBetweenDates);
Thanks guys! :-D
The NSTimeInterval is in seconds. So minutes would be diff/60.0 and hours would be diff/3600.0.
you could do:
NSTimeInterval timeDifference = [secondDate timeIntervalSinceDate:firstDate];
int minute = (int)timeDifference % 3600 / 60;
I have this subset of a method that needs to get day one of the current month.
NSDate *today = [NSDate date]; // returns correctly 28 february 2013
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [[NSDateComponents alloc] init];
components.day = 1;
NSDate *dayOneInCurrentMonth = [gregorian dateByAddingComponents:components toDate:today options:0];
dayOneInCurrentMonth then prints out 2013-03-01 09:53:49 +0000, the first day of the next month.
How do I get day one of the current month?
Your logic is wrong: Instead of setting the date's day to 1, you're adding a day to the current date.
Try something like that:
NSDate *today = [NSDate date];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [gregorian components:(NSEraCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit) fromDate:today];
components.day = 1;
NSDate *dayOneInCurrentMonth = [gregorian dateFromComponents:components];
You want [NSCalender dateFromComponents:] instead:
NSDate *dayOneInCurrentMonth = [gregorian dateFromComponents:components];
Easy way of getting to the 1st from a given date:
NSDate *first = [gregorian dateBySettingUnit:NSCalendarUnitDay value:1 ofDate:date options:0];
Easy Way to get first and last date of previous month is :
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *comp = [gregorian components:(NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay ) fromDate:[NSDate date]];
//TO GET PREVIOUS MONTH LAST DAY
[comp setMonth:[comp month]];
[comp setDay:1];
NSDate *tDateMonth = [gregorian dateFromComponents:comp];
NSLog(#"LAST DAY OF PREVIOUS MONTH ; %#", tDateMonth);
//TO GET PREVIOUS MONTH FIRST DAY
[comp setMonth:[comp month]-1];
[comp setDay:3];
NSDate *td = [gregorian dateFromComponents:comp];
NSLog(#"FIRST DAY OF PREVIOUS MONTH ; %#", td);
Hope this helps
By creating new variable is expensive on memory usage, it's better using date formatter to get the first day of the current month
today = [NSDate date];
firstDayDateFormatter = [[NSDateFormatter alloc] init];
[firstDayDateFormatter setDateFormat:#"01-MM-yyyy"];
dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"dd-MM-yyyy"];
[dateFormatter setLocale:[NSLocale localeWithLocaleIdentifier:#"en_US"]];
firstDayOfTheMonth = [mdfDateFormat dateFromString:[firstDayDateFormatter stringFromDate:today]];
NSDate *startDate = nil;
[[NSCalendar currentCalendar] rangeOfUnit:NSCalendarUnitMonth startDate:&startDate interval:NULL forDate:date];
return startDate;
I'm trying to construct a date from two different dates. When I break down both dates into their respective components and re-assemble them into the new date.. everything seems to be correct except the hours. Im sure its something simple that has to do with the timezone or the NSGregorianCalendar, but I am new to iOS, and programming NSCalendar. Im hoping someone will catch the simple mistake Im making.
//grab today's date so we can brek it down into components
NSDate *todayDate = [NSDate date];
NSLog(#"Todays Date: %#", todayDate);
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
//break down the stored date into components
NSDateComponents *theTime = [gregorian components:(NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:storedIncorrectDate];
NSLog(#"Incorrect Calendar Components %#", theTime);
NSDateComponents *todayCalendarComponents = [gregorian components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:todayDate];
NSInteger currentYear = [todayCalendarComponents year];
NSLog(#"The Year: %i", currentYear);
NSInteger currentMonth = [todayCalendarComponents month];
NSLog(#"The Month: %i", currentMonth);
NSInteger currentDay = [todayCalendarComponents day];
NSLog(#"The Day: %i", currentDay);
NSLog(#"Today's Calendar Components %#", todayCalendarComponents);
NSInteger theHours = [theTime hour];
NSLog(#"Hours: %i", theHours);
NSInteger theMinutes = [theTime minute];
NSLog(#"Minutes: %i", theMinutes);
NSInteger theSeconds = [theTime second];
NSLog(#"Seconds: %i", theSeconds);
//build my new date and store it before we play the affirmation.
NSDateComponents *components = [[NSDateComponents alloc] init];
[components setHour:theHours];
[components setMinute:theMinutes];
[components setSecond:theSeconds];
[components setYear:currentYear];
[components setMonth:currentMonth];
[components setDay:currentDay];
[components setTimeZone:[NSTimeZone localTimeZone]];
NSLog(#"The Components: %#", components);
NSCalendar *updatedCal = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *revisedCorrectedDate = [updatedCal dateFromComponents:components];
NSLog(#"The Hours: %i", theHours);
NSLog(#"The New and Corrected Date: %#", revisedCorrectedDate);
The result of the log printing the revisedCorrectedDate shows everything correct that I set except the hours. This has to be a simple fix.. I just don't see it. Thank you in advance!
Are you sure it's incorrect? When I run this code, I get:
2012-06-03 18:13:36.130 Untitled[39805:707] The New and Corrected
Date: 2012-06-04 01:13:36 +0000
It's currently 6/3/12 18:13:36 here, and the date displayed is 6/4/12 01:13:36, which is the correct time, in UTC (notice the +0000 at the end).
How do I set the time of the DatePicker at 00:00:00 of the current date?
- (void) awakeFromNib
{
[datePicker setDateValue:[NSDate date]];
NSDate *now = [NSDate date];
int daysToAdd = 364;
NSDate *newDate1 = [now dateByAddingTimeInterval:60*60*24*daysToAdd];
[datePicker1 setDateValue:newDate1];
}
cringe
It looks like you have two different datePickers? datePicker and datePicker1? What's up with that?
Also, this does not do what you're expecting:
NSDate *newDate1 = [now dateByAddingTimeInterval:60*60*24*364];
That is creating a new date that is exactly 31,449,600 seconds in the future. It is not doing anything other than that.
What you want to do is extract all of the date components from the current date and zero them out:
NSDate *now = [NSDate date];
NSDateComponents *nowComponents = [[NSCalendar currentCalendar] components:(NSEraCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:now];
// technically these next lines are unnecessary, since we only pulled out the era-year-month-day, but they're included here for understanding/completeness:
[nowComponents setHour:0];
[nowComponents setMinute:0];
[nowComponents setSecond:0];
// now we can turn it back into a date:
NSDate *todayAtMidnight = [[NSCalendar currentCalendar] dateFromComponents:nowComponents];
Is there a better way to do this?
-(NSDate *)getMidnightTommorow {
NSCalendarDate *now = [NSCalendarDate date];
NSCalendarDate *tomorrow = [now dateByAddingYears:0 months:0 days:1 hours:0 minutes:0 seconds:0];
return [NSCalendarDate dateWithYear:[tomorrow yearOfCommonEra]
month:[tomorrow monthOfYear]
day:[tomorrow dayOfMonth]
hour:0
minute:0
second:0
timeZone:[tomorrow timeZone]];
}
Note that I always want the next midnight, even if it happens to be midnight when I make that call, however if it happens to be 23:59:59, I of course want the midnight that is coming in one second.
The natural language functions seem flaky, and I'm not sure what Cocoa would do if I pass 32 in the "day" field. (If that'd work I could drop the [now dateByAddingYears:...] call)
From the documentation:
Use of NSCalendarDate strongly
discouraged. It is not deprecated yet,
however it may be in the next major OS
release after Mac OS X v10.5. For
calendrical calculations, you should
use suitable combinations of
NSCalendar, NSDate, and
NSDateComponents, as described in
Calendars in Dates and Times
Programming Topics for Cocoa.
Following that advice:
NSDate *today = [NSDate date];
NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [[NSDateComponents alloc] init];
components.day = 1;
NSDate *tomorrow = [gregorian dateByAddingComponents:components toDate:today options:0];
[components release];
NSUInteger unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
components = [gregorian components:unitFlags fromDate:tomorrow];
components.hour = 0;
components.minute = 0;
NSDate *tomorrowMidnight = [gregorian dateFromComponents:components];
[gregorian release];
[components release];
(I'm not sure offhand if this is the most efficient implementation, but it should serve as a pointer in the right direction.)
Note: In theory you can reduce the amount of code here by allowing a date components object with values greater than the range of normal values for the component (e.g. simply adding 1 to the day component, which might result in its having a value of 32). However, although dateFromComponents: may tolerate out-of-bounds values, it's not guaranteed to. You're strongly encouraged not to rely on it.
Nope - it'll be the same way you use to find midnight today.
NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:(24 * 60 * 60)];
NSDateComponents *components = [gregorian components:(NSYearCalendarUnit |
NSMonthCalendarUnit |
NSDayCalendarUnit)
fromDate:tomorrow];
NSDate *midnight = [gregorian dateFromComponents:components];
[NSDate dateWithNaturalLanguageString:#"midnight tomorrow"];
Convert your current date and time to a Unix date (seconds since 1970) or DOS style (since 1980), then add 24 hours and convert it back. Then reset the hours, minutes and seconds to zero to get to midnight.
You could try this way:
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *comps = [[NSDateComponents alloc] init];
[comps setDay:1];
NSDate *tomorrow = [calendar dateByAddingComponents:comps toDate:[NSDate date] options:0]; //it gives us tomorrow with current time
NSDate *midnight = [calendar startOfDayForDate:tomorrow]; //here we get next midnight
It is also easy to retrieve the seconds interval if needed to set up an NSTimer:
double intervalToMidnight = midnight.timeIntervalSinceNow;