Getting the last day of a month

How can I get the last day of the current month as an NSDate?

NSDate *curDate = [NSDate date];
NSCalendar* calendar = [NSCalendar currentCalendar];
NSDateComponents* comps = [calendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSWeekCalendarUnit|NSWeekdayCalendarUnit fromDate:curDate]; // Get necessary date components

// set last of month
[comps setMonth:[comps month]+1];
[comps setDay:0];
NSDate *tDateMonth = [calendar dateFromComponents:comps];
NSLog(@"%@", tDateMonth);

should also work.

// Adapted from running code in my app

NSDate *curDate = [NSDate date];
NSCalendar *currentCalendar = [NSCalendar currentCalendar];
NSRange daysRange = 
[currentCalendar 
 rangeOfUnit:NSDayCalendarUnit 
 inUnit:NSMonthCalendarUnit 
 forDate:curDate];

// daysRange.length will contain the number of the last day
// of the month containing curDate

NSLog(@"%i", daysRange.length);

Put this in a category:

-(NSDate*)lastDayOfMonth
{
    NSInteger dayCount = [self numberOfDaysInMonthCount];
    
    NSDateComponents *comp = [[self calendar] components:
                              NSCalendarUnitYear |
                              NSCalendarUnitMonth |
                              NSCalendarUnitDay fromDate:self];
    
    [comp setDay:dayCount];
    
    return [[self calendar] dateFromComponents:comp];
}

-(NSInteger)numberOfDaysInMonthCount
{
    NSRange dayRange = [[self calendar] rangeOfUnit:NSCalendarUnitDay
                                             inUnit:NSCalendarUnitMonth
                                            forDate:self];
    
    return dayRange.length;
}

-(NSCalendar*)calendar
{
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];    
    [calendar setTimeZone:[NSTimeZone timeZoneWithName:TIMEZONE]];
    return calendar;
}

Swift version

extension NSDate {
    func lastDayOfMonth() -> NSDate {
        let calendar = NSCalendar.currentCalendar()
        let dayRange = calendar.rangeOfUnit(.Day, inUnit: .Month, forDate: self)
        let dayCount = dayRange.length
        let comp = calendar.components([.Year, .Month, .Day], fromDate: self)

        comp.day = dayCount

        return calendar.dateFromComponents(comp)!
    }
}

Version from iOS 7

just to get rid of the deprecations... with a minor addition to get the last second of the day.

    // current date
    NSDate *now = [NSDate new];
    
    // get last day of the current month
    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    [calendar setTimeZone:[NSTimeZone systemTimeZone]];
    
    NSRange dayRange = [ calendar rangeOfUnit:NSCalendarUnitDay
                                       inUnit:NSCalendarUnitMonth
                                      forDate:now];
    
    NSInteger numberOfDaysInCurrentMonth = dayRange.length;
    
    NSDateComponents *comp = [calendar components:
                              NSCalendarUnitYear |
                              NSCalendarUnitMonth |
                              NSCalendarUnitDay fromDate:now];
    
    comp.day = numberOfDaysInCurrentMonth;
    comp.hour = 24;
    comp.minute = 0;
    comp.second = 0;
    
    NSDate *endOfMonth = [calendar dateFromComponents:comp];

Swift 3.0.1 Version

extension Date {
func lastDayOfMonth() -> Date {
    let calendar = NSCalendar.current
    let dayRange = calendar.range(of: .day, in: .month, for: self)
    let dayCount = dayRange?.count
    var comp = calendar.dateComponents([.year, .month, .day], from: self)
    comp.day = dayCount
    return calendar.date(from: comp)!
    }
}

With Swift 3 & iOS 10 the easiest way I found to do this is Calendar's dateInterval(of:for:):

func monthInterval() -> DateInterval? {
    let calendar = Calendar.current
    guard let interval = calendar.dateInterval(of: .month, for: Date()) else { return nil }
    let duration = interval.duration
    // Subtract one second because dateInterval(of:for:)'s end date returns the beginning of the following month
    return DateInterval(start: interval.start, duration: duration - 1)
}

guard let interval = monthInterval() else { return }

You can then use interval.start and interval.end to get the dates you need.

NSDate *curDate = [NSDate date];
        NSCalendar *currentCalendar = [NSCalendar currentCalendar];
        NSRange daysRange = [[NSCalendar currentCalendar] rangeOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitMonth
         forDate:curDate];
        NSDateComponents* comps = [currentCalendar components:NSCalendarUnitYear|NSCalendarUnitMonth|NSCalendarUnitDay fromDate:curDate];
        [comps setDay:daysRange.length];
        NSDate *maximumDate = [[NSCalendar currentCalendar] dateFromComponents:comps];

Workaround Function:

-(int)GetLastDayOfMonth:(NSDate *)date
{
	int last_day = 27;
	NSCalendar *cal=[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
	NSDateComponents *compsMonth = [cal components:NSWeekdayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit fromDate:date];
	[compsMonth setDay:last_day];
	int month = [compsMonth month]; 
	while(TRUE){
	    [compsMonth setDay:last_day+1];
		NSDate *dateFuture = [cal dateFromComponents:compsMonth];
		NSDateComponents *futureComps = [cal components:NSWeekdayCalendarUnit | NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit fromDate:dateFuture];
		if(month != [futureComps month]){
			return last_day;
		}
		last_day+=1;
	}
	return last_day;
}