在Swift 4或Swift 5中，你可以使用like bellow:

let date = Date()
let yesterday = Calendar.current.date(byAdding: .day, value: -1, to: date)
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
let yesterday_date = dateFormatter.string(from: yesterday!)
print("yesterday->",yesterday_date)

输出:

Current date: 2020-03-02
yesterday date: 2020-03-01

使用下面的函数，并使用days参数来获取日期daysAhead/daysBehind，只需将参数传递为正，表示未来日期，为负，表示之前日期:

+ (NSDate *) getDate:(NSDate *)fromDate daysAhead:(NSUInteger)days
{
    NSDateComponents *dateComponents = [[NSDateComponents alloc] init];
    dateComponents.day = days;
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDate *previousDate = [calendar dateByAddingComponents:dateComponents
                                                     toDate:fromDate
                                                    options:0];
    [dateComponents release];
    return previousDate;
}

在swift中，您可以在NSDate中添加扩展方法

extension NSDate {
    func addNoOfDays(noOfDays:Int) -> NSDate! {
        let cal:NSCalendar = NSCalendar.currentCalendar()
        cal.timeZone = NSTimeZone(abbreviation: "UTC")!
        let comps:NSDateComponents = NSDateComponents()
        comps.day = noOfDays
        return cal.dateByAddingComponents(comps, toDate: self, options: nil)
    }
}

你可以用这个

NSDate().addNoOfDays(3)

Swift 3.0非常简单的实现将是:

func dateByAddingDays(inDays: Int) -> Date {
    let today = Date()
    return Calendar.current.date(byAdding: .day, value: inDays, to: today)!
}

使用以下代码:

NSDate *now = [NSDate date];
int daysToAdd = 1;
NSDate *newDate1 = [now dateByAddingTimeInterval:60*60*24*daysToAdd];

As

addTimeInterval

现在已弃用。

swift 5更新

let nextDate = fromDate.addingTimeInterval(60*60*24)