效果如下：

ViewController.h

1 #import 
     
      2 3 @interface ViewController : UIViewController4 @property (strong, nonatomic) UIDatePicker *datePChoice;5 6 @end
     

ViewController.m

1 #import "ViewController.h" 2  3 @interface ViewController () 4 - (void)layoutUI; 5 - (void)pickerDidChange:(UIDatePicker *)sender; 6 - (void)buttonDidPush:(UIButton *)sender; 7 @end 8  9 @implementation ViewController10 11 - (void)viewDidLoad {12     [super viewDidLoad];13     14     [self layoutUI];15 }16 17 - (void)didReceiveMemoryWarning {18     [super didReceiveMemoryWarning];19     // Dispose of any resources that can be recreated.20 }21 22 - (void)layoutUI {23     _datePChoice = [[UIDatePicker alloc] initWithFrame:CGRectMake(0, 0, 0, 0)];24     CGPoint newPoint = self.view.center;25     _datePChoice.center = newPoint;26     _datePChoice.datePickerMode = UIDatePickerModeDateAndTime; //默认值是UIDatePickerModeDateAndTime27     [_datePChoice addTarget:self28                      action:@selector(pickerDidChange:) forControlEvents:UIControlEventValueChanged];29     [self.view addSubview:_datePChoice];30     31     UIButton *btnChoice = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 280, 40)];32     newPoint.y += 160;33     btnChoice.center = newPoint;34     btnChoice.layer.masksToBounds = YES;35     btnChoice.layer.cornerRadius = 10.0;36     btnChoice.layer.borderColor = [UIColor colorWithRed:0.655 green:0.619 blue:0.601 alpha:1.000].CGColor;37     btnChoice.layer.borderWidth = 2.0;38     [btnChoice setTitle:@"切换日期选择器框的显示样式" forState:UIControlStateNormal];39     [btnChoice setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];40     [btnChoice addTarget:self41                   action:@selector(buttonDidPush:)42         forControlEvents:UIControlEventTouchUpInside];43     [self.view addSubview:btnChoice];44 }45 46 - (void)pickerDidChange:(UIDatePicker *)sender {47     NSLog(@"%@", [_datePChoice.date description]); //2015-04-19 11:00:03 +0000；显示时区少了8个钟，所以用NSDateFormatter显示的时间才算正常时区时间48 }49 50 - (void)buttonDidPush:(UIButton *)sender {51     //设置日期选择器框的显示样式52     static NSInteger i = 1;53     switch (i%4) {54         case 0:55             _datePChoice.datePickerMode = UIDatePickerModeDateAndTime; //UI效果：4月19日 周日 下午 7 0056             break;57         case 1:58             _datePChoice.datePickerMode = UIDatePickerModeDate; //UI效果：2005年 4月 19日59             break;60         case 2:61             _datePChoice.datePickerMode = UIDatePickerModeTime; //UI效果：下午 7 0062             break;63         case 3:64             _datePChoice.datePickerMode = UIDatePickerModeCountDownTimer; //UI效果：0hours 1min65             break;66     }67     i++;68 }69 70 @end