dateFromString return nil.

NSDateFormatter *dm = [[NSDateFormatter alloc] init];
[dm setDateFormat:@"yyyy-MM-dd HH:mm"];
NSString* dateTimeStr = [NSString stringWithFormat:@"%@ %@",_date, _time];
NSDate *sourceDate = [dm dateFromString:dateTimeStr];

(lldb) po dateTimeStr

2014-12-01 00:00

(lldb) po dm

<NSDateFormatter: 0x17005c470>

放狗搜：

If the device is set to AM/PM time and requested string format is set to @"yyyy-MM-dd HH:mm:ss" dateFromString will return nil.

If you set the locale to @"en_US" conversion will return correct date.

dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setTimeZone:[NSTimeZone timeZoneWithName:@"GMT"]];
[dateFormat setLocale:[[NSLocale alloc] initWithLocaleIdentifier:@"en_US"]];
[dateFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *date = [dateFormat dateFromString:@"2013-02-14 09:30:00"];

复现条件：真机

地区调成：英国UK

时间格式调成：12小时制

语言：英语