How to Find the Number of Days in Given Month and Year Using Swift

How do I find the number of days in given month and year using swift

First create an NSDate for the given year and month:

let dateComponents = NSDateComponents()
dateComponents.year = 2015
dateComponents.month = 7

let calendar = NSCalendar.currentCalendar()
let date = calendar.dateFromComponents(dateComponents)!

Then use the rangeOfUnit() method, as described in
Number of days in the current month using iPhone SDK?:

// Swift 2:
let range = calendar.rangeOfUnit(.Day, inUnit: .Month, forDate: date)
// Swift 1.2:
let range = calendar.rangeOfUnit(.CalendarUnitDay, inUnit: .CalendarUnitMonth, forDate: date)

let numDays = range.length
print(numDays) // 31

Update for Swift 3 (Xcode 8):

let dateComponents = DateComponents(year: 2015, month: 7)
let calendar = Calendar.current
let date = calendar.date(from: dateComponents)!

let range = calendar.range(of: .day, in: .month, for: date)!
let numDays = range.count
print(numDays) // 31

How to calculate the number of days in the current month/year

Here is a method which works for both months and years:

let calendar = NSCalendar.currentCalendar()
let date = NSDate()

// Calculate start and end of the current year (or month with `.Month`):
var startOfInterval : NSDate?
var lengthOfInterval = NSTimeInterval()
calendar.rangeOfUnit(.Year, startDate: &startOfInterval, interval: &lengthOfInterval, forDate: date)
let endOfInterval = startOfInterval!.dateByAddingTimeInterval(lengthOfInterval)

// Compute difference in days:
let days = calendar.components(.Day, fromDate: startOfInterval!, toDate: endOfInterval, options: [])
print(days)

(You may want to add some error checking instead of forcibly unwrapping
optionals.)

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Update for Swift 3:

let calendar = Calendar.current
let date = Date()

// Calculate start and end of the current year (or month with `.month`):
let interval = calendar.dateInterval(of: .year, for: date)!

// Compute difference in days:
let days = calendar.dateComponents([.day], from: interval.start, to: interval.end).day!
print(days)

Number of days in the current month using iOS?

You can use the NSDate and NSCalendar classes:

NSDate *today = [NSDate date]; //Get a date object for today's date
NSCalendar *c = [NSCalendar currentCalendar];
NSRange days = [c rangeOfUnit:NSDayCalendarUnit 
                       inUnit:NSMonthCalendarUnit 
                      forDate:today];

today is an NSDate object representing the current date; this can be used to work out the number of days in the current month. An NSCalendar object is then instantiated, which can be used, in conjunction with the NSDate for the current date, to return the number of days in the current month using the rangeOfUnit:inUnit:forDate: function.

days.length will contain the number of days in the current month.

Here are the links to the docs for NSDate and NSCalendar if you want more information.

Get the Previous Month days count

These is the usage :

let calendar = Calendar.current
let date1 = calendar.date(byAdding: .month, value: -1, to: Date())! // -1 mean previous month

let range = calendar.range(of: .day, in: .month, for: date1)!
let numDays = range.count
print(numDays)

OUTPUT :

31

Calculating the number of days between two dates in swift

It has to do with the order that you're creating your variables and comparing them.

The first thing you do is create today. Then, you create twoWeeksFromNow, based on a new Date() that will be slightly further in the future than today was. On my machine, in a playground, the second date is about 300 microseconds further in the future than the first.

Then, for numDaysWithDate, you compare twoWeeksFromNow to another new Date(), even more slightly in the future. So, your time frame is very slightly less than 2 full weeks, giving you 13 days.

But, for numDaysWithToday, you compare twoWeeksFromNow with the original today, which was created before twoWeeksFromNow was, making it slightly longer than 2 weeks, giving you 14 days.

If you change the order of the the today and twoWeeksFromNow declarations, you can see a different result:

var twoWeeksFromNow: Date = Calendar.current.date(byAdding: .day,
value: 14, to: Date())!
var today = Date()

Now, because today was created slightly later than the date that twoWeeksFromNow was created from, both results are 13.

How can we get all the days in selected month

You can get the range of day in the month, and map the range initializing a new date using the year and month components of the date combined with the day from the range. I am using noon time because not every date starts at 12am:

extension Date {
    func datesInSameMonth(using calendar: Calendar = .current) -> [Date] {
        let year = calendar.component(.year, from: self)
        let month = calendar.component(.month, from: self)
        return calendar.range(of: .day, in: .month, for: self)?.compactMap {
            DateComponents(calendar: calendar, year: year, month: month, day: $0, hour: 12).date
        } ?? []
    }
}

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print(Date().datesInSameMonth())  // [2020-09-01 15:00:00 +0000, 2020-09-02 15:00:00 +0000, 2020-09-03 15:00:00 +0000, 2020-09-04 15:00:00 +0000, 2020-09-05 15:00:00 +0000, 2020-09-06 15:00:00 +0000, 2020-09-07 15:00:00 +0000, 2020-09-08 15:00:00 +0000, 2020-09-09 15:00:00 +0000, 2020-09-10 15:00:00 +0000, 2020-09-11 15:00:00 +0000, 2020-09-12 15:00:00 +0000, 2020-09-13 15:00:00 +0000, 2020-09-14 15:00:00 +0000, 2020-09-15 15:00:00 +0000, 2020-09-16 15:00:00 +0000, 2020-09-17 15:00:00 +0000, 2020-09-18 15:00:00 +0000, 2020-09-19 15:00:00 +0000, 2020-09-20 15:00:00 +0000, 2020-09-21 15:00:00 +0000, 2020-09-22 15:00:00 +0000, 2020-09-23 15:00:00 +0000, 2020-09-24 15:00:00 +0000, 2020-09-25 15:00:00 +0000, 2020-09-26 15:00:00 +0000, 2020-09-27 15:00:00 +0000, 2020-09-28 15:00:00 +0000, 2020-09-29 15:00:00 +0000, 2020-09-30 15:00:00 +0000]

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