iPhone SDK Tip: 获取当前日期和时间

获取系统日期和时间：

- (NSString *)nowTime{

NSDate *date = [NSDate date];

NSCalendar *calendar = [NSCalendar currentCalendar];

NSDateComponents *comps;

comps = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit) fromDate:date];

return [NSString stringWithFormat:@"%.4d-%.2d-%.2d %.2d:%.2d:%.2d",[comps year],[comps month],[comps day],[comps hour],[comps minute],[comps second]];

}