objective - c:

NSDate *date = [NSDate dateWithTimeIntervalSinceNow:0];
NSDateFormatter *formatter = [NSDateFormatter new];
formatter.dateFormat = @"yyyy";
NSString *dateString = [formatter stringFromDate:date];

迅速:

let now = Date()
let formatter = DateFormatter()
formatter.dateFormat = "yyyy"
let dateString = formatter.string(from: now) 

这是nsdateformatter的一个好网站。您可以在不同的本地使用不同的DateFormatter预览日期字符串。

NSCalendar *calendar = [NSCalendar currentCalendar];
NSDateComponents *components = [calendar components:(NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay) fromDate:myNSDateInstance];
NSInteger year = [components year];
// NSInteger month = [components month];
NSString *yearStr = [NSString stringWithFormat:@"%ld", year];

  NSDateFormatter *dateformate=[[NSDateFormatter alloc]init];
  [dateformate setDateFormat:@"yyyy"]; // Date formater
  NSString *date = [dateformate stringFromDate:[NSDate date]]; // Convert date to string
  NSLog(@"date :%@",date);

定义您自己的实用程序格式的日期所需的日期格式 如。

NSString * stringFromDate(NSDate *date)  
 {   NSDateFormatter *formatter
    [[NSDateFormatter alloc] init];  
    [formatter setDateFormat:@"MM ∕ dd ∕ yyyy, hh꞉mm a"];    
    return [formatter stringFromDate:date]; 
}

+(NSString*)date2str:(NSDate*)myNSDateInstance onlyDate:(BOOL)onlyDate{
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    if (onlyDate) {
        [formatter setDateFormat:@"yyyy-MM-dd"];
    }else{
        [formatter setDateFormat: @"yyyy-MM-dd HH:mm:ss"];
    }

    //Optionally for time zone conversions
    //   [formatter setTimeZone:[NSTimeZone timeZoneWithName:@"..."]];

    NSString *stringFromDate = [formatter stringFromDate:myNSDateInstance];
    return stringFromDate;
}

+(NSDate*)str2date:(NSString*)dateStr{
    if ([dateStr isKindOfClass:[NSDate class]]) {
        return (NSDate*)dateStr;
    }

    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"yyyy-MM-dd"];
    NSDate *date = [dateFormat dateFromString:dateStr];
    return date;
}

iOS 15更新

iOS 15现在支持直接在Date对象上调用.格式化，而不需要显式的DateFormatter。

常见格式示例

文档

date.formatted() // 6/8/2021, 7:30 PM
date.formatted(date: .omitted, time: .complete) // 19:30
date.formatted(date: .omitted, time: .standard) // 07:30 PM
date.formatted(date: .omitted, time: .shortened) // 7:30 PM
date.formatted(date: .omitted, time: .omitted)

替代语法

文档

// We can also specify each DateComponent separately by chaining modifiers.
date.formatted(.dateTime.weekday(.wide).day().month().hour().minute())
// Tuesday, Jun 8, 7:30 pm

// Answer to specific question
date.formatted(.dateTime.year())