iOS 获取当前时间及时间戳的互换

1. 获取年月日时分秒

NSDate *date1 = [NSDate date];

NSDateFormatter *formatter1 = [[NSDateFormatter alloc] init];

[formatter1 setDateStyle:NSDateFormatterMediumStyle];

[formatter1 setTimeStyle:NSDateFormatterShortStyle];

[formatter1 setDateFormat:@"YYYY-MM-dd hh:mm:ss"];

NSString *DateTime1 = [formatter1 stringFromDate:date1];

str就是我们需要的时间，代码中("YYYY-MM-dd HH:mm:ss")这个时间的样式是可以根据我们的需求进行修改的，比如： 20170901112253 ==> ("YYYYMMddHHmmss")

如果只想获取年月，代码如下：

NSDate *date1 = [NSDate date];

NSDateFormatter *formatter1 = [[NSDateFormatter alloc] init];

[formatter1 setDateStyle:NSDateFormatterMediumStyle];

[formatter1 setTimeStyle:NSDateFormatterShortStyle];

[formatter1 setDateFormat:@"YYYY-MM"];

NSString *DateTime1 = [formatter1 stringFromDate:date1];

2. 区分系统时间是24小时制还是12小时制

//获取系统是24小时制或者12小时制

NSString *formatStringForHours = [NSDateFormatter dateFormatFromTemplate:@"j" options:0 locale:[NSLocale currentLocale]];

NSRange contains = [formatStringForHours rangeOfString:@"a"];

BOOL thisAMPM = contains.location != NSNotFound;

thisAMPM == true //表示12小时制 否则为24小时制

3. 字符串转时间戳

//字符串转时间戳

//datenow为当前时间

NSString *timeSp = [NSString stringWithFormat:@"%d", (long)[datenow timeIntervalSince1970]];

//时间戳的值

NSLog(@"timeSp:%@",timeSp);

4.时间戳转字符串

//时间戳转字符串

NSString *timeStr = "1506064573";

NSTimeInterval interval=[timeStr doubleValue] / 1000.0;

NSDate *date = [NSDate dateWithTimeIntervalSince1970:interval];

//实例化一个NSDateFormatter对象

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

//设定时间格式,这里可以设置成自己需要的格式

[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

NSString *currentDateStr = [dateFormatter stringFromDate:date];