简单的方法，使用c#风格的方式将日期转换为字符串。

用法:

let a = time.asString()
// 1990-03-25


let b = time.asString("MM ∕ dd ∕ yyyy, hh꞉mm a")
// 03 / 25 / 1990, 10:33 PM

扩展:

extension Date {
    func asString(_ template: String? = nil) -> String {
        if let template = template {
            let df = DateFormatter.with(template: template)
            
            return df.string(from: self)
        }
        else {
            return globalDateFormatter.string(from: self)
        }
    }
}

// Here you can set default template for DateFormatter
public let globalDateFormatter: DateFormatter = DateFormatter.with(template: "y-M-d")

public extension DateFormatter {
    static func with(template: String ) -> DateFormatter {
        let df = DateFormatter()
        df.dateFormat = template
        return df
    }
}

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。

迅速回答

static let dateformat: String = "yyyy-MM-dd'T'HH:mm:ss"
public static func stringTodate(strDate : String) -> Date
{

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = dateformat
    let date = dateFormatter.date(from: strDate)
    return date!
}
public static func dateToString(inputdate : Date) -> String
{

    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = dateformat
    return formatter.string(from: inputdate)

}

希望通过提供包括年、月、日和时间的正常格式化程序来增加更多的价值。 您可以使用这个格式化程序超过一年

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

+(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;
}

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];