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POObjective C: Converting string to nsdate issue
 

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  1. POObjective C: Converting string to nsdate issue
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    <p>I spent couple of hours to resolve this weird issue. I have date formate in "dd/mm/yyyy hh:mm:ss" and want to know the difference in seconds between my date and NOW. I am doing it like below but not getting why it is getting 31 days wrong? It should be just few hours difference! Could anyone please help me what am I doing wrong here?</p> <pre><code>NSString* datetime = @"03/02/2012 10:25:34"; // Today's date NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease]; [dateFormatter setDateFormat:@"dd/mm/yyyy hh:mm:ss"]; NSDate *dateFromString = [dateFormatter dateFromString:datetime]; NSTimeInterval diffSeconds = [[NSDate date] timeIntervalSinceDate:dateFromString]; int totalDays = diffSeconds/(24*60*60); NSLog(@"seconds:%f totaldays:%d",diffSeconds, totalDays); </code></pre> <p>OUTPUT:</p> <pre><code>2012-02-03 10:50:50.480 UniversalApp[13114:707] diff:2679916.480563 totaldays:31 </code></pre> <p>Then I tried to convert dateFromString to NSDate again and I surprised it printed totally random date. Not sure how is following possible? It should give my original date "datetime"!</p> <pre><code>NSDateFormatter* formatter = [[[NSDateFormatter alloc] init] autorelease]; [formatter setDateFormat:@"dd/mm/yyyy hh:mm:ss"]; NSString* str = [formatter stringFromDate:dateFromString]; NSLog(@"date:%@ to date:%@", datetime, str); </code></pre> <p>OUTPUT:</p> <pre><code>date:03/02/2012 10:25:34 to date:03/25/2012 10:25:34 </code></pre> <p>[EDIT]</p> <p>Replacing "dd/mm/yyyy hh:mm:ss" to "dd/MM/yyyy hh:mm:ss" worked but still seconds difference is not coming correct. See following outputs for different dates!</p> <p>Corrected Code:</p> <pre><code>NSLog(@"For Date:%@",[res objectForKey:@"CommentDate"]); NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease]; [dateFormatter setDateFormat:@"dd/MM/yyyy hh:mm:ss"]; NSDate *dateFromString = [dateFormatter dateFromString:[res objectForKey:@"CommentDate"]]; NSTimeInterval diffSeconds = [[NSDate date] timeIntervalSinceDate:dateFromString]; int totalDays = diffSeconds/(24*60*60); NSLog(@"seconds:%f totaldays:%d",diffSeconds, totalDays); </code></pre> <p>OUTPUT: (notice many outputs are Nan!!)</p> <p>2012-02-03 11:30:23.198 UniversalApp[13207:707] For Date:03/02/2012 10:25:34</p> <p>2012-02-03 11:30:23.204 UniversalApp[13207:707] seconds:3889.204166 totaldays:0</p> <p>2012-02-03 11:30:23.506 UniversalApp[13207:707] For Date:02/02/2012 16:56:05</p> <p>2012-02-03 11:30:23.512 UniversalApp[13207:707] seconds:nan totaldays:0</p> <p>2012-02-03 11:30:23.818 UniversalApp[13207:707] For Date:02/02/2012 14:34:05</p> <p>2012-02-03 11:30:23.827 UniversalApp[13207:707] seconds:nan totaldays:0</p> <p>2012-02-03 11:31:25.253 UniversalApp[13207:707] ToDate: 02/02/2012 12:02:55</p> <p>2012-02-03 11:31:25.255 UniversalApp[13207:707] seconds:127710.255748 totaldays:1</p> <p>2012-02-03 11:32:06.424 UniversalApp[13207:707] For Date:01/02/2012 11:01:20</p> <p>2012-02-03 11:32:06.427 UniversalApp[13207:707] seconds:174646.427676 totaldays:2</p> <p>2012-02-03 11:32:06.639 UniversalApp[13207:707] For Date:31/01/2012 17:38:17</p> <p>2012-02-03 11:32:06.643 UniversalApp[13207:707] seconds:nan totaldays:0</p> <p>[EDIT]</p> <p>Replacing 'hh' with 'HH' resolved above issue!</p> <p>[EDIT]</p> <p>Another issue I ran into...phew!!</p> <p>This doesn't work if set 24 hours clock off! Based on <a href="https://stackoverflow.com/questions/2135267/nsdateformatter-with-24-hour-times">this</a>, it overrides by the user's settings.</p> <p>I couldn't find any strong solution for this last issue. Finally I decided to check for 'nan' value for seconds and if it is 'nan' then use original date string and don't convert into seconds, hours etc.</p> <pre><code>// Check for the 'nan', return if seconds='nan' invalid date format. if(seconds != seconds) return nil; </code></pre> <p>// Proceed to do your work</p>
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