只是为了好玩，通过一些扩展和操作符重载，你可以得到一些不错的东西，比如:

let today = Date()
let tomorrow = today + 1.days

, or

var date = Date()
date += 1.months

下面是支持代码:

extension Calendar {
    struct ComponentWithValue {
        let component: Component
        let value: Int
    }
}

extension Int {
    var days: Calendar.ComponentWithValue {
        .init(component: .day, value: self)
    }
    
    var months: Calendar.ComponentWithValue {
        .init(component: .month, value: self)
    }
}

func +(_ date: Date, _ amount: Calendar.ComponentWithValue) -> Date {
    Calendar.current.date(byAdding: amount.component, value: amount.value, to: date)!
}

func +(_ amount: Calendar.ComponentWithValue, _ date: Date) -> Date {
    date + amount
}

func +=(_ date: inout Date, _ amount: Calendar.ComponentWithValue) {
    date = date + amount
}

代码是最少的，并且可以很容易地扩展到允许.月，.年，.小时等。还可以无缝添加对减法(-)的支持。

虽然在+操作符的实现中有一个强制的展开，但是不确定在哪种情况下日历可以返回nil日期。

斯威夫特4.0

extension Date {
    func add(_ unit: Calendar.Component, value: Int) -> Date? {
        return Calendar.current.date(byAdding: unit, value: value, to: self)
    }
}

使用

date.add(.day, 3)!   // adds 3 days
date.add(.day, -14)!   // subtracts 14 days

注意:如果你不知道为什么代码行以感叹号结尾，可以在谷歌上查找“Swift optional”。

斯威夫特5

let today = Date()
let nextDate = Calendar.current.date(byAdding: .day, value: 1, to: today)

objective - c

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
// now build a NSDate object for the next day
NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
[offsetComponents setDay:1];
NSDate *nextDate = [gregorian dateByAddingComponents:offsetComponents toDate: [NSDate date] options:0];

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。

斯威夫特2.0

let today = NSDate()    
let calendar = NSCalendar.currentCalendar()
let tomorrow = calendar.dateByAddingUnit(.Day, value: 1, toDate: today, options: NSCalendarOptions.MatchFirst)

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

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"EEEE, dd MMM yyyy"];
NSLog(@"%@", [dateFormatter stringFromDate:tomorrowDate]);