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PONSCalendar: Problem getting weeks in a month
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copied!<p>I am creating a calendar control of sorts...</p> <p>One thing I need to know is how many weeks are there in a Month...</p> <p>So <code>NSCalendar</code> <code>rangeOfUnit:inUnit:forDate</code> Seems to be exactly what I need...</p> <p>Except I am noticing something that seems off and I can't quite figure out why this is happening...</p> <p>The following code...</p> <pre><code>NSCalendar *calendar = [NSCalendar currentCalendar]; NSDateComponents *dateComponents = [[NSDateComponents alloc] init]; [dateComponents setYear: 2010]; [dateComponents setDay: 1]; for (int x=1; x<=12; x++) { [dateComponents setMonth: x]; NSDate *date = [calendar dateFromComponents:dateComponents]; NSLog(@"Date: %@", date); NSRange range = [calendar rangeOfUnit: NSWeekCalendarUnit inUnit: NSMonthCalendarUnit forDate:date]; NSLog(@"%d Weeks in Month %d", range.length, [dateComponents month]); } </code></pre> <p>Is returning the following debug messages...</p> <pre><code>2010-03-14 13:08:10.350 Scrap[4256:207] Date: 2010-01-01 00:00:00 -0500 2010-03-14 13:08:10.351 Scrap[4256:207] 5 Weeks in Month 1 2010-03-14 13:08:10.352 Scrap[4256:207] Date: 2010-02-01 00:00:00 -0500 2010-03-14 13:08:10.352 Scrap[4256:207] 4 Weeks in Month 2 2010-03-14 13:08:10.353 Scrap[4256:207] Date: 2010-03-01 00:00:00 -0500 2010-03-14 13:08:10.353 Scrap[4256:207] 5 Weeks in Month 3 2010-03-14 13:08:10.354 Scrap[4256:207] Date: 2010-04-01 00:00:00 -0400 2010-03-14 13:08:10.355 Scrap[4256:207] 5 Weeks in Month 4 2010-03-14 13:08:10.356 Scrap[4256:207] Date: 2010-05-01 00:00:00 -0400 2010-03-14 13:08:10.357 Scrap[4256:207] 5 Weeks in Month 5 2010-03-14 13:08:10.358 Scrap[4256:207] Date: 2010-06-01 00:00:00 -0400 2010-03-14 13:08:10.358 Scrap[4256:207] 5 Weeks in Month 6 2010-03-14 13:08:10.359 Scrap[4256:207] Date: 2010-07-01 00:00:00 -0400 2010-03-14 13:08:10.360 Scrap[4256:207] 5 Weeks in Month 7 2010-03-14 13:08:10.361 Scrap[4256:207] Date: 2010-08-01 00:00:00 -0400 2010-03-14 13:08:10.364 Scrap[4256:207] 5 Weeks in Month 8 2010-03-14 13:08:10.364 Scrap[4256:207] Date: 2010-09-01 00:00:00 -0400 2010-03-14 13:08:10.365 Scrap[4256:207] 5 Weeks in Month 9 2010-03-14 13:08:10.366 Scrap[4256:207] Date: 2010-10-01 00:00:00 -0400 2010-03-14 13:08:10.366 Scrap[4256:207] 5 Weeks in Month 10 2010-03-14 13:08:10.367 Scrap[4256:207] Date: 2010-11-01 00:00:00 -0400 2010-03-14 13:08:10.367 Scrap[4256:207] 5 Weeks in Month 11 2010-03-14 13:08:10.369 Scrap[4256:207] Date: 2010-12-01 00:00:00 -0500 2010-03-14 13:08:10.369 Scrap[4256:207] 52 Weeks in Month 12 </code></pre> <p>I cant quite figure out why I get 52 weeks in month 12.</p> <p>Any clues?</p> <p>Edit on 3/20/2010:</p> <p>Seeing as how I couldnt use <code>rangeOfUnit:inUnit:forDate</code> to calculate the number of weeks in a month. I decided to figure out a different way of calculating the same value.</p> <p>I figured I should do this in a non-Gregorian localized way, so I attempted to start with getting the number of days in a week, but I got the result of 28 days in a week. So I started writing more code to figure out why...</p> <p>I wanted to make sure that the type of NSCalendar that I was playing with was in fact what I was supposed to be getting... And that led me to finding some differences...</p> <pre><code>NSCalendar *currentCalendar = [NSCalendar currentCalendar]; NSLog(@"Calendar with 'currentCalendar' Identifier: %@", [currentCalendar calendarIdentifier]); NSCalendar *calendarWithIdentifier = [[[NSCalendar alloc] initWithCalendarIdentifier: NSGregorianCalendar] autorelease]; NSLog(@"Calendar created with identifier Identifier: %@", [calendarWithIdentifier calendarIdentifier]); NSDate *now = [[NSDate alloc] init]; NSDateComponents *currentMonth = [currentCalendar components: NSMonthCalendarUnit | NSYearCalendarUnit fromDate: now]; NSDate *currentMonthDate = [currentCalendar dateFromComponents: currentMonth]; NSRange daysInWeekRange = [currentCalendar rangeOfUnit: NSDayCalendarUnit inUnit: NSWeekCalendarUnit forDate: currentMonthDate]; NSLog(@"CurrentCalendar: Length:%u Location:%u", daysInWeekRange.length, daysInWeekRange.location); currentMonth = [calendarWithIdentifier components: NSMonthCalendarUnit | NSYearCalendarUnit fromDate: now]; currentMonthDate = [calendarWithIdentifier dateFromComponents: currentMonth]; daysInWeekRange = [calendarWithIdentifier rangeOfUnit: NSDayCalendarUnit inUnit: NSWeekCalendarUnit forDate: currentMonthDate]; NSLog(@"GregorianCalendar: Length:%u Location:%u", daysInWeekRange.length, daysInWeekRange.location); </code></pre> <p>And that got me the following log results...</p> <pre><code>2010-03-20 21:02:27.245 Scrap[52189:207] Calendar with 'currentCalendar' Identifier: gregorian 2010-03-20 21:02:27.246 Scrap[52189:207] Calendar created with identifier Identifier: gregorian 2010-03-20 21:02:27.248 Scrap[52189:207] CurrentCalendar: Length:28 Location:1 2010-03-20 21:02:27.249 Scrap[52189:207] GregorianCalendar: Length:7 Location:1 </code></pre> <p>Taking direction from @CarlNorum's experience, I compiled the code snippet as a 10.6 Cocoa application, and I got the following...</p> <pre><code>2010-03-20 21:05:35.636 ScrapCocoa[52238:a0f] Calendar with 'currentCalendar' Identifier: gregorian 2010-03-20 21:05:35.636 ScrapCocoa[52238:a0f] Calendar created with identifier Identifier: gregorian 2010-03-20 21:05:35.637 ScrapCocoa[52238:a0f] CurrentCalendar: Length:6 Location:1 2010-03-20 21:05:35.638 ScrapCocoa[52238:a0f] GregorianCalendar: Length:7 Location:1 </code></pre> <p>I saw hope in that creating a NSCalendar Instance explicitly as a Gregorian Calendar would lead to better results in my original problem... So I modified that original code</p> <pre><code>NSCalendar *currentCalendar = [NSCalendar currentCalendar]; NSLog(@"Calendar with 'currentCalendar' Identifier: %@", [currentCalendar calendarIdentifier]); NSCalendar *calendarWithIdentifier = [[[NSCalendar alloc] initWithCalendarIdentifier: NSGregorianCalendar] autorelease]; NSLog(@"Calendar created with identifier Identifier: %@", [calendarWithIdentifier calendarIdentifier]); NSDateComponents *dateComponents = [[[NSDateComponents alloc] init] autorelease]; [dateComponents setYear: 2010]; [dateComponents setDay: 1]; for (int x=1; x<=12; x++) { [dateComponents setMonth: x]; NSDate *date = [currentCalendar dateFromComponents: dateComponents]; NSRange range = [currentCalendar rangeOfUnit: NSWeekCalendarUnit inUnit: NSMonthCalendarUnit forDate: date]; NSLog(@"CurrentCalendar Date: %@", date); NSLog(@"CurrentCalendar: %d Weeks in Month %d", range.length, [dateComponents month]); date = [calendarWithIdentifier dateFromComponents: dateComponents]; range = [calendarWithIdentifier rangeOfUnit: NSWeekCalendarUnit inUnit: NSMonthCalendarUnit forDate: date]; NSLog(@"GregorianCalendar Date: %@", date); NSLog(@"GregorianCalendar: %d Weeks in Month %d", range.length, [dateComponents month]); } </code></pre> <p>Unfortunately using a calendar created that way did not return a different result.</p> <pre><code>2010-03-20 21:15:40.465 Scrap[52367:207] Calendar with 'currentCalendar' Identifier: gregorian 2010-03-20 21:15:40.466 Scrap[52367:207] Calendar created with identifier Identifier: gregorian 2010-03-20 21:15:40.468 Scrap[52367:207] CurrentCalendar Date: 2010-01-01 00:00:00 -0500 2010-03-20 21:15:40.468 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 1 2010-03-20 21:15:40.469 Scrap[52367:207] GregorianCalendar Date: 2010-01-01 00:00:00 -0500 2010-03-20 21:15:40.470 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 1 2010-03-20 21:15:40.471 Scrap[52367:207] CurrentCalendar Date: 2010-02-01 00:00:00 -0500 2010-03-20 21:15:40.471 Scrap[52367:207] CurrentCalendar: 4 Weeks in Month 2 2010-03-20 21:15:40.472 Scrap[52367:207] GregorianCalendar Date: 2010-02-01 00:00:00 -0500 2010-03-20 21:15:40.473 Scrap[52367:207] GregorianCalendar: 4 Weeks in Month 2 2010-03-20 21:15:40.473 Scrap[52367:207] CurrentCalendar Date: 2010-03-01 00:00:00 -0500 2010-03-20 21:15:40.474 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 3 2010-03-20 21:15:40.475 Scrap[52367:207] GregorianCalendar Date: 2010-03-01 00:00:00 -0500 2010-03-20 21:15:40.475 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 3 2010-03-20 21:15:40.476 Scrap[52367:207] CurrentCalendar Date: 2010-04-01 00:00:00 -0400 2010-03-20 21:15:40.477 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 4 2010-03-20 21:15:40.478 Scrap[52367:207] GregorianCalendar Date: 2010-04-01 00:00:00 -0400 2010-03-20 21:15:40.479 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 4 2010-03-20 21:15:40.480 Scrap[52367:207] CurrentCalendar Date: 2010-05-01 00:00:00 -0400 2010-03-20 21:15:40.480 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 5 2010-03-20 21:15:40.482 Scrap[52367:207] GregorianCalendar Date: 2010-05-01 00:00:00 -0400 2010-03-20 21:15:40.482 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 5 2010-03-20 21:15:40.483 Scrap[52367:207] CurrentCalendar Date: 2010-06-01 00:00:00 -0400 2010-03-20 21:15:40.483 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 6 2010-03-20 21:15:40.484 Scrap[52367:207] GregorianCalendar Date: 2010-06-01 00:00:00 -0400 2010-03-20 21:15:40.485 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 6 2010-03-20 21:15:40.485 Scrap[52367:207] CurrentCalendar Date: 2010-07-01 00:00:00 -0400 2010-03-20 21:15:40.486 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 7 2010-03-20 21:15:40.486 Scrap[52367:207] GregorianCalendar Date: 2010-07-01 00:00:00 -0400 2010-03-20 21:15:40.487 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 7 2010-03-20 21:15:40.488 Scrap[52367:207] CurrentCalendar Date: 2010-08-01 00:00:00 -0400 2010-03-20 21:15:40.488 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 8 2010-03-20 21:15:40.489 Scrap[52367:207] GregorianCalendar Date: 2010-08-01 00:00:00 -0400 2010-03-20 21:15:40.489 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 8 2010-03-20 21:15:40.490 Scrap[52367:207] CurrentCalendar Date: 2010-09-01 00:00:00 -0400 2010-03-20 21:15:40.491 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 9 2010-03-20 21:15:40.491 Scrap[52367:207] GregorianCalendar Date: 2010-09-01 00:00:00 -0400 2010-03-20 21:15:40.492 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 9 2010-03-20 21:15:40.493 Scrap[52367:207] CurrentCalendar Date: 2010-10-01 00:00:00 -0400 2010-03-20 21:15:40.493 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 10 2010-03-20 21:15:40.494 Scrap[52367:207] GregorianCalendar Date: 2010-10-01 00:00:00 -0400 2010-03-20 21:15:40.494 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 10 2010-03-20 21:15:40.495 Scrap[52367:207] CurrentCalendar Date: 2010-11-01 00:00:00 -0400 2010-03-20 21:15:40.496 Scrap[52367:207] CurrentCalendar: 5 Weeks in Month 11 2010-03-20 21:15:40.496 Scrap[52367:207] GregorianCalendar Date: 2010-11-01 00:00:00 -0400 2010-03-20 21:15:40.497 Scrap[52367:207] GregorianCalendar: 5 Weeks in Month 11 2010-03-20 21:15:40.498 Scrap[52367:207] CurrentCalendar Date: 2010-12-01 00:00:00 -0500 2010-03-20 21:15:40.498 Scrap[52367:207] CurrentCalendar: 52 Weeks in Month 12 2010-03-20 21:15:40.499 Scrap[52367:207] GregorianCalendar Date: 2010-12-01 00:00:00 -0500 2010-03-20 21:15:40.500 Scrap[52367:207] GregorianCalendar: 52 Weeks in Month 12 </code></pre> <p>Compiling the code for Cocoa just for kicks, was actually amusing... As the results are really really different</p> <pre><code>2010-03-20 21:11:24.610 ScrapCocoa[52313:a0f] Calendar with 'currentCalendar' Identifier: gregorian 2010-03-20 21:11:24.611 ScrapCocoa[52313:a0f] Calendar created with identifier Identifier: gregorian 2010-03-20 21:11:24.613 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-01-01 00:00:00 -0500 2010-03-20 21:11:24.613 ScrapCocoa[52313:a0f] CurrentCalendar: 6 Weeks in Month 1 2010-03-20 21:11:24.614 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-01-01 00:00:00 -0500 2010-03-20 21:11:24.615 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 1 2010-03-20 21:11:24.616 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-02-01 00:00:00 -0500 2010-03-20 21:11:24.616 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 2 2010-03-20 21:11:24.617 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-02-01 00:00:00 -0500 2010-03-20 21:11:24.618 ScrapCocoa[52313:a0f] GregorianCalendar: 4 Weeks in Month 2 2010-03-20 21:11:24.619 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-03-01 00:00:00 -0500 2010-03-20 21:11:24.619 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 3 2010-03-20 21:11:24.620 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-03-01 00:00:00 -0500 2010-03-20 21:11:24.621 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 3 2010-03-20 21:11:24.622 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-04-01 00:00:00 -0400 2010-03-20 21:11:24.622 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 4 2010-03-20 21:11:24.623 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-04-01 00:00:00 -0400 2010-03-20 21:11:24.623 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 4 2010-03-20 21:11:24.624 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-05-01 00:00:00 -0400 2010-03-20 21:11:24.625 ScrapCocoa[52313:a0f] CurrentCalendar: 6 Weeks in Month 5 2010-03-20 21:11:24.625 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-05-01 00:00:00 -0400 2010-03-20 21:11:24.626 ScrapCocoa[52313:a0f] GregorianCalendar: 6 Weeks in Month 5 2010-03-20 21:11:24.627 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-06-01 00:00:00 -0400 2010-03-20 21:11:24.627 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 6 2010-03-20 21:11:24.628 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-06-01 00:00:00 -0400 2010-03-20 21:11:24.628 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 6 2010-03-20 21:11:24.629 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-07-01 00:00:00 -0400 2010-03-20 21:11:24.630 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 7 2010-03-20 21:11:24.630 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-07-01 00:00:00 -0400 2010-03-20 21:11:24.631 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 7 2010-03-20 21:11:24.632 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-08-01 00:00:00 -0400 2010-03-20 21:11:24.632 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 8 2010-03-20 21:11:24.633 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-08-01 00:00:00 -0400 2010-03-20 21:11:24.633 ScrapCocoa[52313:a0f] GregorianCalendar: 6 Weeks in Month 8 2010-03-20 21:11:24.634 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-09-01 00:00:00 -0400 2010-03-20 21:11:24.635 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 9 2010-03-20 21:11:24.636 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-09-01 00:00:00 -0400 2010-03-20 21:11:24.636 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 9 2010-03-20 21:11:24.637 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-10-01 00:00:00 -0400 2010-03-20 21:11:24.637 ScrapCocoa[52313:a0f] CurrentCalendar: 6 Weeks in Month 10 2010-03-20 21:11:24.638 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-10-01 00:00:00 -0400 2010-03-20 21:11:24.639 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 10 2010-03-20 21:11:24.640 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-11-01 00:00:00 -0400 2010-03-20 21:11:24.640 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 11 2010-03-20 21:11:24.641 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-11-01 00:00:00 -0400 2010-03-20 21:11:24.641 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 11 2010-03-20 21:11:24.642 ScrapCocoa[52313:a0f] CurrentCalendar Date: 2010-12-01 00:00:00 -0500 2010-03-20 21:11:24.642 ScrapCocoa[52313:a0f] CurrentCalendar: 5 Weeks in Month 12 2010-03-20 21:11:24.643 ScrapCocoa[52313:a0f] GregorianCalendar Date: 2010-12-01 00:00:00 -0500 2010-03-20 21:11:24.644 ScrapCocoa[52313:a0f] GregorianCalendar: 5 Weeks in Month 12 </code></pre> <p>I think this is when I give up...</p>

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