NSDate for first day of the month

Question

This is quite a simple concept, but as of yet I have been unable to find an elegant (and calendar locale independent) solution. I need to find the first day of the month for

Answer 1

A possible solution:

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *arbitraryDate = [NSDate date];
NSDateComponents *comp = [gregorian components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:arbitraryDate];
[comp setDay:1];
NSDate *firstDayOfMonthDate = [gregorian dateFromComponents:comp];

Answer 2

Swift 3

I've included getting the last day of the month in case it is useful to anyone.

extension Date {
    func lastDayOfMonth() -> Date {
        let calendar = Calendar.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)!
    }

    func firstDayOfMonth() -> Date {
        let calendar: Calendar = Calendar.current
        var components: DateComponents = calendar.dateComponents([.year, .month, .day], from: self)
        components.setValue(1, for: .day)
        return calendar.date(from: components)!
    }
}

Answer 3

Swift version

let arbitraryDate:NSDate = NSDate()
let calendar:NSCalendar = NSCalendar.currentCalendar()
let components:NSDateComponents = calendar.components([.Year, .Month, .Day], fromDate: arbitraryDate)
components.setValue(1, forComponent: .Day)
let firstDayOfMonthDate = calendar.dateFromComponents(components)

Answer 4

NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear 
                                                               fromDate:[NSDate date]];
components.day = 1;
NSDate *firstDayOfMonthDate = [[NSCalendar currentCalendar] dateFromComponents: components];
NSLog(@"First day of month: %@", [firstDayOfMonthDate descriptionWithLocale:[NSLocale currentLocale]]);

Answer 5

Swift 3:

let calendar = Calendar.current
var comps = calendar.dateComponents([.year, .month], from: date)
comps.setValue(1, for: .day)
let firstDayOfMonth = calendar.date(from: comps)!

// I tried this, but it doesn't work, why?
// let firstDayOfMonth = calendar.date(bySetting: .day, value: 1, of: date)!