swift 5更新

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

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;
}

简单的Swift扩展昨天和明天从任何日期:

extension Date {
    
    var previousDay: Date {
        Calendar.current.date(byAdding: DateComponents(day:-1), to: self)!
    }
    
    var nextDay: Date {
        Calendar.current.date(byAdding: DateComponents(day:+1), to: self)!
    }
    
}

我在这里根据问题中的建议强制展开可选选项: 何时dateByAddingComponents:toDate:options返回nil?

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)

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”。

它的工作原理!

NSCalendar *calendar = [NSCalendar currentCalendar];
NSCalendarUnit unit = NSCalendarUnitDay;
NSInteger value = 1;
NSDate *today = [NSDate date];
NSDate *tomorrow = [calendar dateByAddingUnit:unit value:value toDate:today options:NSCalendarMatchStrictly];