如何……

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy"];

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

NSString *stringFromDate = [formatter stringFromDate:myNSDateInstance];

//unless ARC is active
[formatter release];

Swift 4.2:

func stringFromDate(_ date: Date) -> String {
    let formatter = DateFormatter()
    formatter.dateFormat = "dd MMM yyyy HH:mm" //yyyy
    return formatter.string(from: date)
}

我不知道为什么我们都错过了这个:localizedStringFromDate:dateStyle:timeStyle:

NSString *dateString = [NSDateFormatter localizedStringFromDate:[NSDate date] 
                                                      dateStyle:NSDateFormatterShortStyle 
                                                      timeStyle:NSDateFormatterFullStyle];
NSLog(@"%@",dateString);

输出'13/06/12 00:22:39 GMT+ 00:00 '

如果你在Mac OS X上，你可以这样写:

NSString* s = [[NSDate date] descriptionWithCalendarFormat:@"%Y_%m_%d_%H_%M_%S" timeZone:nil locale:nil];

但是这在iOS上是不可用的。

#ios #swift #convertDateinString

简单地像这样按你传递的格式“将日期转换为字符串”:

let formatter = DateFormatter()

formatter.dateFormat = "dd-MM-YYYY" // pass formate here
        
let myString = formatter.string(from: date) // this will convert Date in String

注意:你可以指定不同的格式，如"yyyy-MM-dd"， "yyyy"， "MM"等。

+(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;
}

只需添加这个扩展:

extension NSDate {
    var stringValue: String {
        let formatter = NSDateFormatter()
        formatter.dateFormat = "yourDateFormat"
        return formatter.stringFromDate(self)
    }
}