Generating random date of current month

Question

I want to get a random date of the current month.

Is there any easy way to get the random date of the month?

use random function for number of days in current month – DivineDesert Jul 09 '12 at 04:39 — DivineDesert, Jul 09 '12 at 04:39

DivineDesert · Accepted Answer · 2012-07-09T05:02:16.040

14

NSDate *today = [NSDate date]; 
NSCalendar *calendar = [NSCalendar currentCalendar];
NSCalendarUnit unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
NSDateComponents *dateComponents = [calendar components:unitFlags fromDate:today];
NSRange days = [calendar rangeOfUnit:NSDayCalendarUnit 
                       inUnit:NSMonthCalendarUnit 
                      forDate:today];

To generate random number, use

int r = arc4random() % days.length;

and then create a date

[dateComponents setDay:r];
NSDate *startDate = [calendar dateFromComponents:dateComponents];

Hope this helps :)

edited Jul 09 '12 at 05:02

answered Jul 09 '12 at 04:42

DivineDesert

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I was about to suggest the edit you made (re: components and creating the actual date...) +1! – Chris Trahey Jul 09 '12 at 04:54
Note that for a better distribution random_uniform() should be used. See this comments for more details: http://stackoverflow.com/a/7082580/751268 – Scott Berrevoets Jul 09 '12 at 04:56
Ok this is good one. But will you please tell me in last line of answer the meaning of `c` in `[c dateFromComponents:dateComponents];` – The iOSDev Jul 09 '12 at 05:01
That is calendar, that was my mistake – DivineDesert Jul 09 '12 at 05:02

score 3 · Answer 2 · answered Jan 18 '21 at 06:21

Swift version:

let date = Date()
let calendar = Calendar.current
var dateComponents = calendar.dateComponents([.year, .month, .day], from: date)
guard
    let days = calendar.range(of: .day, in: .month, for: date),
    let randomDay = days.randomElement()
else {
        return nil
}
dateComponents.setValue(randomDay, for: .day)
return calendar.date(from: dateComponents)

Generating random date of current month

2 Answers2