I need to show only seven days from now. How to achieve this using UIDatePicker and how we set minimum and maximum dates to UIDatePicker. Thanks in advance.
[datePicker setMinimumDate:[NSDate date]];
[datePicker setMaximumDate:[NSDate dateWithTimeIntervalSinceNow:60*60*24*7]];
He wants only seven days including current date.
A small caution against overly simplistic addition of time: simply adding seconds can encounter edge cases against daylight savings time transitions (for example). It is always a good idea to use NSCalendar to help manage time calculations.
NSDate *today = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
calendar.timeZone = [NSTimeZone localTimeZone];
NSDate *endDate = [calendar dateByAddingUnit:NSCalendarUnitDay value:7 toDate:today options:0];
The resulting endDate in the above code will be one hour different than simply adding seconds, in the case of daylight savings time occurring during the 7 day period. That one hour could break across a day change, causing a (rare) edge case failure.
Set Min and Max date in the datePicker:
[datePicker setMinimumDate:[NSDate date];
[datePicker setMaximumDate:[[NSDate date] dateByAddingTimeInterval:60*60*24*7]];
Related
I want to get how many seconds are remaining to complete an hour. No matter which what time it is?
if its 05:01:00 then it should give 3540 seconds
and if its 11:58:40 then it gives 80 seconds and so on. I try to find it on google but could not able to find it.
Thanks in advance.
NSCalendar has got methods to do that kind of date math:
NSDate *now = [NSDate date];
NSCalendar *calendar = [NSCalendar currentCalendar];
// find next date where the minutes are zero
NSDate *nextHour = [calendar nextDateAfterDate:now matchingUnit:NSCalendarUnitMinute value:0 options:NSCalendarMatchNextTime];
// get the number of seconds between now and next hour
NSDateComponents *componentsToNextHour = [calendar components:NSCalendarUnitSecond fromDate:now toDate:nextHour options:0];
NSLog(#"%ld", componentsToNextHour.second);
#Vadian's answer is very good. (voted)
It requires iOS 8 or later however.
There are other ways you could do this using NSCalendar and NSDateComponents that would work with older OS versions.
You could use componentsFromDate to get the month, day, year, and hour from the current date, then increment the hour value and use the NSCalendar method dateFromComponents: to convert your to adjusted components back to a date.
NSDate *date1 = [NSDate dateWithString:#"2010-01-01 00:00:00 +0000"];
NSDate *date2 = [NSDate dateWithString:#"2010-02-03 00:00:00 +0000"];
NSTimeInterval secondsBetween = [date2 timeIntervalSinceDate:date1];
Fill in with the correct times and dates to get the difference in seconds
Edit: An alternative method is to work out the currenthour and return as an integer. Then add one to the NSInteger returned as below (you will have to make sure to handle the case where it is after midnight though!)
NSDateComponents *components = [[NSCalendar currentCalendar] components:NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit fromDate:[NSDate date]];
NSInteger currentHour = [components hour];
I am making an app to use at school and I want to make a countdown timer to countdown the amount of time between now and the end of school, which for me is 3:00. For example, at 11:15, it will read 3:45.
So far, I have figured out how to make the countdown timer and I have the following code: countdownTimer.text = [Formatter stringFromDate: [NSDate date]];
This code doesn't actually work yet, but I think it will work if I figure out how to subtract the current time from a set time and then use that value where date is, however I am open to other suggestions on how to approach the problem.
You can use NSCalendar method dateBySettingHour:minute:second: to get the NSDate object associated with 3pm today:
NSCalendar *calendar = [NSCalendar currentCalendar];
NSDate *now = [NSDate date];
NSDate *schoolOut = [calendar dateBySettingHour:15 minute:0 second:0 ofDate:now options:0];
There are lots of different ways to get the NSDate object associated with 3pm today, but the above is just one example. You could also use components:fromDate of NSCalendar to extract the NSDateComponents of now, then adjust the hour, minute and second and then create a new NSDate object using dateFromComponents (also a NSCalendar method).
Anyway, once you have a NSDate object that represents your target date/time, you can then use NSDateComponentsFormatter to display the time interval between two dates in a nice format.
NSDateComponentsFormatter *formatter = [[NSDateComponentsFormatter alloc] init];
formatter.allowedUnits = NSCalendarUnitHour | NSCalendarUnitMinute;
formatter.unitsStyle = NSDateComponentsFormatterUnitsStyleFull;
formatter.zeroFormattingBehavior = NSDateComponentsFormatterZeroFormattingBehaviorPad;
NSString *string = [formatter stringFromDate:now toDate:schoolOut];
You can adjust the unitsStyle and zeroFormattingBehavior to adjust the format of the string.
I'm trying to write an application that will send the user an alert in the Notification Center 60 hours before the date arrives. Here is the code:
localNotif.fireDate = [eventDate dateByAddingTimeInterval:-60*60*60];
I was wondering if the -60*60*60 formula will work to alert them 60 hours prior to the date? I'm not sure at all how the formula works, I would like to set it up to alert 10 minutes before the date for testing purposes, then change it back to 60 hours once I confirm that everything is correct. Does any one know the formula to use for both of these?
Any help is much appreciated, thank you!
A crude but easy-to-code way is to add/subtract seconds from an NSDate directly:
NSDate *hourLaterDate = [date dateByAddingTimeInterval: 60*60];
NSDate *hourEarlierDate = [date dateByAddingTimeInterval: -60*60];
You can see how it works by logging the dates:
NSDate *now = [NSDate date];
NSDate *hourLaterDate = [now dateByAddingTimeInterval: 60*60];
NSLog(#"%# => %#", now, hourLaterDate);
In this approach a date is interpreted as a number of seconds since the reference date. So, internally it's just a big number of type double.
A tedious-to-code but pedantically correct way to do these calculations is by interpreting dates as dates expressed in a calendar system. The same thing achieved as calendrical calculations:
NSDateComponents *hour = [[NSDateComponents alloc] init];
[hour setHour: 1];
NSCalendar *calendar= [[NSCalendar alloc] initWithCalendarIdentifier: NSGregorianCalendar];
NSDate *hourLaterDate = [calendar dateByAddingComponents: hour
toDate: date
options: 0];
[hour release];
[calendar release];
These calculations take into account time zones, daylight saving time, leap years, etc. They can also be more expressive in terms of what you're calculating.
Before using any of these approaches you have to decide what exactly you need: a timestamp or a full-blown calendar date.
Is there any way to find out an accurate difference between two NSDate?
I have found solutions but they aren't accurate enough. I need to take into account daylight saving, the fact that different months have a different number of days, etc.
A simple calculation such as /60/60/24 etc. to work out minutes, hours and days doesn't take them into account.
Lets say I need to work out the difference between the time right now ([NSDate date]) and December 25th 10:22PM (date chosen by user using date picker [datePicker date]) just as an example, how would I do this?
Knowing the exact time difference isn't the key, so long as I have an accurate difference of days, months and years, it will do.
From Apple's Date & Time Programming Guide:
Listing 12 Getting the difference between two dates
NSDate *startDate = ...;
NSDate *endDate = ...;
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar];
NSUInteger unitFlags = NSMonthCalendarUnit | NSDayCalendarUnit;
NSDateComponents *components = [gregorian components:unitFlags
fromDate:startDate
toDate:endDate options:0];
NSInteger months = [components month];
NSInteger days = [components day];
NSDate is completely independent of Timezone. Daylight saving doesn't even come into the picture for NSDate. Only when you convert NSDate into a human readable format (MM/DD/YY, HH:MM:SS format or the like), does Time Zone come into picture.
Make sure that you take into account correct timezone, day-light saving setting when you create NSDate(s). Subsequently, the method, [date1 timeIntervalSinceDate:date2] should always give you accurate time difference.
So, the more accurate question you meant to ask was: How can I get a nicely formatted days, months, years from a difference between two dates. First you want to get the nsTimerInterval (time difference in seconds) and then format it:
How do I break down an NSTimeInterval into year, months, days, hours, minutes and seconds on iPhone?
Small update on the code for latest iOS:
NSDate *startDate = ...;
NSDate *endDate = ...;
NSCalendar *gregorian = [[NSCalendar alloc]
initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSUInteger unitFlags = NSCalendarUnitMonth | NSCalendarUnitDay;
NSDateComponents *components = [gregorian components:unitFlags
fromDate: startDate
toDate:endDate options:0];
NSInteger months = [components month];
NSInteger days = [components day];
I have been racking my brains on this one looking for a quick solution.
I need to fire off a NSTime at a specific time based on the current time in a specific time zone.
For example, I get the current time in PST:
NSDate *now = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = #"HH:mm:ss";
NSCalendar * cal = [[NSCalendar alloc] initWithCalendarIdentifier: NSGregorianCalendar];
[cal setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"PST"]];
NSDateComponents * comps = [cal components:NSHourCalendarUnit fromDate:now];
I see that the time is 2 (14) getting [comps hour] and I need to fire a timer at 2:30PM (14:30) on that day. I need help converting it back and doing the math to say how long it is before the timer fires. I will be setting up several different timers based on the current time. While I am looking at the time in PST I know that the timers and setting of the time is done in GMT. That's another twist...
Thanks in advance...
I solved the problem myself.. But thanks for the tips...
if ([date earlierDate:newDate] == date) // it is before 7AM... fire at 7AM
and so on....