NSData NSDateFormatter获取当前时间常用功能总结

参考IOS8 SDK

IOS提供获取当前时间的方法，包含日期date和time，可以设置显示的格式（系统和自定义）和地区时间。

1、获取当前时间的方法（可以更改locale我理解不同地区的时间）

1.1获取当前时间，格式显示默认

系统自带时间显示格式

NSDateFormatterNoStyle：不会显示日期和时间

NSDateFormatterShortStyle ：11/29/14, 10:46 PM

NSDateFormatterMediumStyle :Nov 23, 1937” or “3:30:32 PM

NSDateFormatterLongStyle:November 23, 1937” or “3:30:32 PM PST

NSDateFormatterFullStyle:Tuesday, April 12, 1952 AD” or “3:30:42 PM Pacific Standard Time

//把时间NSDate 转换成字符串stringFormatter
    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    formatter.dateStyle = NSDateFormatterShortStyle;//NSDateFormatterNoStyle;
    formatter.timeStyle = NSDateFormatterShortStyle;//NSDateFormatterNoStyle;
    NSString *str = [formatter stringFromDate:[NSDate date]];
  
    str = [NSString stringWithFormat:@"current time is %@", str];
    //配合
    //str = [NSString stringWithFormat:@"Date for locale is %@ %@",[[formatter locale]localeIdentifier],str];
    NSLog(@"log -------- %@",str);
    //output:log -------- current time is 11/29/14, 10:46 PM

获取本地化封装信息，时间地区

[[NSLocale currentLocale]localeIdentifier]

1.2 以1 January 2001, GMT为起始点计算显示时间，可以指定时间地区

 NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    formatter.dateStyle = NSDateFormatterMediumStyle;//NSDateFormatterShortStyle;//NSDateFormatterNoStyle;
    formatter.timeStyle = NSDateFormatterMediumStyle;//NSDateFormatterShortStyle;//NSDateFormatterNoStyle;
    //以秒为单位指定距离参考时间的时间
    NSDate *currentdate = [NSDate dateWithTimeIntervalSinceReferenceDate:118860];
    //设置时间地区
    NSLocale *currentlocale = [[NSLocale alloc]initWithLocaleIdentifier:@"en_US"];
    [formatter setLocale:currentlocale];
    //把时间NSDate 转换成字符串stringFormatter
    NSString *str = [formatter stringFromDate:currentdate];
    
    str = [NSString stringWithFormat:@"current locale is %@ current time is %@",[[NSLocale currentLocale]localeIdentifier], str];
    NSLog(@"log -------- %@",str);
    //output:log -------- current locale is en_US current time is Jan 2, 2001, 5:01:00 PM

1.3有限自定义时间显示格式

Pattern	Result (in a particular locale)
yyyy.MM.dd G 'at' HH:mm:ss zzz	1996.07.10 AD at 15:08:56 PDT
EEE, MMM d, ''yy	Wed, July 10, '96
h:mm a	12:08 PM
hh 'o''clock' a, zzzz	12 o'clock PM, Pacific Daylight Time
K:mm a, z	0:00 PM, PST
yyyyy.MMMM.dd GGG hh:mm aaa	01996.July.10 AD 12:08 PM

http://www.unicode.org/reports/tr35/tr35-31/tr35-dates.html#Date_Format_Patterns

    NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
    //formatter.dateStyle = NSDateFormatterMediumStyle;//NSDateFormatterShortStyle;//NSDateFormatterNoStyle;
    //formatter.timeStyle = NSDateFormatterMediumStyle;//NSDateFormatterShortStyle;//NSDateFormatterNoStyle;
    //以秒为单位指定距离参考时间的时间
   // NSDate *currentdate = [NSDate dateWithTimeIntervalSinceReferenceDate:118860];
    //设置时间地区
   // NSLocale *currentlocale = [[NSLocale alloc]initWithLocaleIdentifier:@"en_US"];
   // [formatter setLocale:currentlocale];
    //把时间NSDate 转换成字符串stringFormatter
    [formatter setDateFormat:@"yyyy.MM.dd G 'at' HH:mm:ss zzz"];
    NSString *str = [formatter stringFromDate:[NSDate date]];
    
    str = [NSString stringWithFormat:@"current locale is %@ current time is %@",[[NSLocale currentLocale]localeIdentifier], str];
    NSLog(@"log -------- %@",str);
    //output:log -------- current locale is en_US current time is 2014.11.30 AD at 08:33:13 GMT+8