I have seen many version of the following code to remove the time element from an NSDate.
NSCalendar *cal = [NSCalendar currentCalendar];
NSDate *now = [NSDate date];
unsigned int intFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit;
NSDateComponents *components = [cal components:intFlags fromDate:now];
NSDate *today = [cal dateFromComponents:components];
Trouble is it does not work as expected. I am currently in British summertime (BST). If I run this code now, now=#"2012-07-07 19:24:06 +0000"
today=#"2012-07-06 23:00:00 +0000"
What I want to see is today=#"2012-07-07 00:00:00 +0000"
I can only guess that it has something to do with daylight saving. Any ideas?
You are getting midnight BST (which is GMT+1 hour), which is the same as 23:00 GMT (+0000).
[NSDate date] will return a date in the current timezone, so your date is in BST. Have you also tried setting the timezone to GMT:
[components setTimeZone:[NSTimeZone timeZoneWithName:#"GMT"]];
There is no such thing as a date without a time, because there never was a point in time that did not have a time (according to our current calendaring systems, anyway), and a date is just a point in time. Ergo, a date necessarily must have a time.
What you can do, is format a date such that the time isn't displayed. For that, you use an NSDateFormatter:
NSDate *date = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSEraCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date];
NSDate *todayAtMidnight = [calendar dateFromComponents:components];
NSString *formatted = [NSDateFormatter localizedStringFromDate:todayAtMidnight dateStyle: NSDateFormatterMediumStyle];
// "formatted" is now something like "Jul 8, 2012".
// It varies according to your locale and user settings.
Technically the first bit (of setting the time portion to midnight) isn't necessary if you're just formatting a date without the time, but you can leave it in if it makes you feel like you're actually "removing the time". :)
Add a
[components setHour:0];
[components setMinute:0];
[components setSecond:0];
to avoid the use of the default values. Documentation doesn't even say what these values are, so they might not be "0".
Related
I am trying to calculate number of days in current month
today = [NSDate date];
NSLog(#"%#", today);
//calculate how much days in current month
NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSRange days = [cal rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:today];
NSUInteger numberOfDaysInMonth = days.length;
NSLog(#"%d Days in month:%i", numberOfDaysInMonth, NSMonthCalendarUnit);
// end calculating
In log it shows August month instead of May
Why it happens? What I missed?
Thanks
2013-05-07 21:39:01.344 NsTimer[89023:c07] 2013-05-07 18:39:01 +0000
2013-05-07 21:39:01.345 NsTimer[89023:c07] 31 Days in month:8
ANSWER:
Thanks #artur
This is a right code
today = [NSDate date];
NSLog(#"%#", today);
//calculate how much days in current month
NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
int units = NSMonthCalendarUnit;
NSDateComponents *comps = [cal components:units fromDate:today];
NSRange days = [cal rangeOfUnit:NSDayCalendarUnit inUnit:NSMonthCalendarUnit forDate:today];
NSUInteger numberOfDaysInMonth = days.length;
NSLog(#"%d Days in month:%i", numberOfDaysInMonth, comps.month);
// end calculating
Log now shows:
2013-05-07 22:25:04.855 NsTimer[89623:c07] 2013-05-07 19:25:04 +0000
2013-05-07 22:25:04.856 NsTimer[89623:c07] 31 Days in month:5
You log NSMonthCalendarUnit as integer (%i). It is just enum flag value, accidentally 8. To show month number, you should extract it with [[calendar components:NSMonthCalendarUnit fromDate:today] month].
Given an arbitrary date, I need to find the date of the first day of the next week of the month. Note that it is not as simple as adding 7 days to the current date because the last week of the month may be less than 7 days. Here is the code I'm using now:
NSCalendar* calendar = [NSCalendar currentCalendar];
NSDateComponents* components = [calendar components:NSWeekOfMonthCalendarUnit|NSYearCalendarUnit|NSMonthCalendarUnit|NSWeekCalendarUnit|NSDayCalendarUnit fromDate:currentDate];
NSLog(#"week of month: %ld", [components weekOfMonth]);
[components setWeekOfMonth:[components weekOfMonth] + 1];
NSLog(#"new week of month: %ld", [components weekOfMonth]); //week of month is now 2
[components setWeekday:1];
NSDate *nextWeek = [calendar dateFromComponents:components];
As an example, currentDate is set to 2012-10-01. In this example nextWeek is always 2012-10-01. It appears that sending setWeekOfMonth: does not increment the other date components in the NSDateComponents object. Do I have the wrong date components configured, or is setWeekOfMonth: not supposed to work like that?
So.... Let's start with an NSDate and an NSCalendar:
NSDate *date = ...;
NSCalendar *cal = [NSCalendar currentCalendar];
Figure out what day of the week that date is:
NSInteger weekdayOfDate = [cal ordinalityOfUnit:NSWeekdayCalendarUnit inUnit:NSWeekCalendarUnit forDate:date];
NSInteger numberOfDaysToStartOfCurrentWeek = weekdayOfDate - 1;
Let's move that date into the next week:
NSDateComponents *oneWeek = [[NSDateComponents alloc] init];
[oneWeek setWeek:1]; // add one week
[oneWeek setDay:-numberOfDaysToStartOfCurrentWeek]; // ... and subtract a couple of days to get the first day of the week
NSDate *startOfNextWeek = [cal dateByAddingComponents:oneWeek toDate:date options:0];
At this point, you have a date that points to the first day of the next week. Now we should verify that it's still in the same month:
NSDateComponents *monthOfNextWeek = [cal components:NSMonthCalendarUnit fromDate:startOfNextWeek];
NSDateComponents *monthOfThisWeek = [cal components:NSMonthCalendarUnit fromDate:date];
if ([monthOfNextWeek month] != [monthOfThisWeek month]) {
// the first day of the next week is not in the same month as the start date
}
When I run this, I get that the start of next week is 30 Dec 2012 (a Sunday, because my calendar's weeks start on Sunday).
If, however, I want the first day of the week to start on Monday, I can preface this code with:
[cal setFirstWeekday:2]; // the first day of the week is the second day (ie, Monday, because Sunday = 1)
If I do this, then the startOfNextWeek results in 31 Dec 2012.
Will this be a valid answer :
NSDateFormatter *dateFormatter=[NSDateFormatter new];
[dateFormatter setLocale:[[NSLocale alloc]initWithLocaleIdentifier:#"en_US_POSIX"]];
[dateFormatter setDateFormat:#"EEE"];
NSDate *date=[NSDate date];
NSString *dateString=[dateFormatter stringFromDate:date];
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier: NSGregorianCalendar];
NSDateComponents *components = [NSDateComponents new];
[calendar setFirstWeekday:1];//1 for Mon
NSDate *newDate=date;
while (![dateString isEqualToString:#"Mon"]) {
components.day = 1;
newDate = [calendar dateByAddingComponents:components toDate:newDate options:0];
dateString=[dateFormatter stringFromDate:newDate];
}
NSLog(#"Upcoming week Date=%#",newDate);
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];
I’m trying to create a date in the BC era, but failing pretty hard. The following returns ‘4713’ as the year, instead of ‘-4712’:
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [NSDateComponents new];
[components setYear: -4712];
NSDate *date = [calendar dateFromComponents:components];
NSLog(#"%d", [[calendar components:NSYearCalendarUnit fromDate: date] year]);
Any idea what I’m doing wrong?
UPDATE: Working code
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [NSDateComponents new];
[components setYear: -4712];
NSDate *date = [calendar dateFromComponents:components];
NSDateComponents *newComponents = [calendar components:NSEraCalendarUnit|NSYearCalendarUnit fromDate:date];
NSLog(#"Era: %d, year %d", [newComponents era], [newComponents year]);
This prints 0 for the era, just as Ben explained.
Your code is actually working fine. Since there’s no year zero, -4712 is the year 4713 BC. If you check the era component you’ll see that it’s zero, which in the Gregorian calendar indicates BC. Flip that negative sign and you’ll see 4712 AD (era 1).
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;