Swift 日期处理类库 Timepiece

Swift 日期处理类库 Timepiece，可对日期进行加减运算、初始设置、变更、格式化和解析。

示例代码：

加减

let now = NSDate()
let nextWeek = now + 1.week
let dayAfterTomorrow = now + 2.days

// shortcuts #1
let today = NSDate.today()
let tomorrow = NSDate.tomorrow()
let yesterday = NSDate.yesterday()

// shortcuts #2
let dayBeforeYesterday = 2.days.ago
let tokyoOlympicYear = 5.years.later

5.minutes.later.stringFromFormat("yyyy-MM-dd HH:mm:SS")
//=> "2015-03-01 12:05:00"

"1987-06-02".dateFromFormat("yyyy-MM-dd")
//=> NSDate.date(year: 1987, month: 6, day: 2)