NSDate

// 1.获取时间

NSDate *date = [NSDate date];

NSLog(@"%@", date);

// 2.时间格式化

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

dateFormatter.dateFormat = @"yyyy年MM月dd日 HH时mm分ss秒";

NSString *res = [dateFormatter stringFromDate:date];

NSLog(@"res = %@", res);

/****字符串转时间****/

NSString *str = @"2017-01-21 15:28:58 +0000";

NSDateFormatter *strDateFormatter = [[NSDateFormatter alloc] init];

strDateFormatter.dateFormat = @"yyyy-MM-dd- HH-mm-ss Z";

NSDate *strDate = [strDateFormatter dateFromString:str];

NSLog(@"strDate = %@", strDate);