parsing date works on simulator not iphone?

I have the following code to parse a date from string:

NSString * str = @"8/13开发者_C百科/2010 1:59:00 PM";
NSDateFormatter * dateFormat2 = [[NSDateFormatter alloc] init];
[dateFormat2 setDateFormat:@"MM/dd/yyyy h:mm:ss a"];
NSDate * orderDate = [dateFormat2 dateFromString:str ];

but orderDate is always coming up null, what am i doing wrong ? What is the proper dateFormatString ?

This works fine in the emulator but is null on iphone 4 ios 4.0

using this fix from @Liam 's comment helped me fix this, i'm just posting in case its helpful to someone else,

NSDateFormatter * parser = [[NSDateFormatter alloc] init];
NSLocale * locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"]autorelease];
[parser setLocale:locale ];
[parser setFormatterBehavior:NSDateFormatterBehavior10_4];
[parser setDateFormat:@"M/d/yyyy h:mm:ss a"];

NSDate * orderDate = [parser dateFromString:str ];

i realized this bug i found only happens when the iphone user sets their clock to the 24 hour military time,

The problem isn't the date format, it's that the init method is only supported on Mac OS X v10.4 through Mac OS X v10.5 (which is probably why it works in the simulator). Try using

initWithDateFormat:allowNaturalLanguage:

instead. See here for more information.