以月/天/小时/分钟/秒计算两个nsdate之间的差异

I am trying to get the difference between the current date as NSDate() and a date from a PHP time(); call for example: NSDate(timeIntervalSinceReferenceDate: 1417147270). How do I go about getting the difference in time between the two dates. I'd like to have a function that compares the two dates and if(seconds > 60) then it returns minutes, if(minutes > 60) return hours and if(hours > 24) return days and so on.

我正在尝试从PHP time()中获取当前日期NSDate()和日期之间的差异;调用例如:NSDate(timeintervalfide eferencedate: 1417147270)。我怎样才能得到这两次约会之间的时差。我想要一个函数来比较这两个日期和if(秒> 60)然后它返回分钟，if(分钟> 60)返回小时以及if(小时> 24)返回天等等。

How should I go about this?

我该怎么做呢?

EDIT: The current accepted answer has done exactly what I've wanted to do. I recommend it for easy usage for getting the time between two dates in the form that that PHP time() function uses. If you aren't particularly familiar with PHP, that's the time in seconds from January 1st, 1970. This is beneficial for a backend in PHP. If perhaps you're using a backend like NodeJS you might want to consider some of the other options you'll find below.

编辑:当前被接受的答案已经完成了我想做的事情。我建议使用PHP time()函数使用的形式，以便在两个日期之间获取时间。如果你对PHP不是特别熟悉，那就是从1970年1月1日开始的秒数。这对于PHP的后端非常有用。如果您正在使用NodeJS这样的后端，您可能需要考虑下面的一些其他选项。

14 个解决方案

#1

Xcode 9.3 • Swift 4.1

Xcode 9.3•Swift 4.1

You can use Calendar to help you create an extension to do your date calculations as follow:

你可以使用日历来帮助你创建一个扩展来计算你的日期，如下所示:

extension Date {
    /// Returns the amount of years from another date
    func years(from date: Date) -> Int {
        return Calendar.current.dateComponents([.year], from: date, to: self).year ?? 0
    }
    /// Returns the amount of months from another date
    func months(from date: Date) -> Int {
        return Calendar.current.dateComponents([.month], from: date, to: self).month ?? 0
    }
    /// Returns the amount of weeks from another date
    func weeks(from date: Date) -> Int {
        return Calendar.current.dateComponents([.weekOfMonth], from: date, to: self).weekOfMonth ?? 0
    }
    /// Returns the amount of days from another date
    func days(from date: Date) -> Int {
        return Calendar.current.dateComponents([.day], from: date, to: self).day ?? 0
    }
    /// Returns the amount of hours from another date
    func hours(from date: Date) -> Int {
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }
    /// Returns the amount of minutes from another date
    func minutes(from date: Date) -> Int {
        return Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
    }
    /// Returns the amount of seconds from another date
    func seconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.second], from: date, to: self).second ?? 0
    }
    /// Returns the amount of nanoseconds from another date
    func nanoseconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.nanosecond], from: date, to: self).nanosecond ?? 0
    }
    /// Returns the a custom time interval description from another date
    func offset(from date: Date) -> String {
        if years(from: date)   > 0 { return "\(years(from: date))y"   }
        if months(from: date)  > 0 { return "\(months(from: date))M"  }
        if weeks(from: date)   > 0 { return "\(weeks(from: date))w"   }
        if days(from: date)    > 0 { return "\(days(from: date))d"    }
        if hours(from: date)   > 0 { return "\(hours(from: date))h"   }
        if minutes(from: date) > 0 { return "\(minutes(from: date))m" }
        if seconds(from: date) > 0 { return "\(seconds(from: date))s" }
        if nanoseconds(from: date) > 0 { return "\(nanoseconds(from: date))ns" }
        return ""
    }
}

---

Using Date Components Formatter

使用日期组件格式化程序

let dateComponentsFormatter = DateComponentsFormatter()
dateComponentsFormatter.allowedUnits = [.year,.month,.weekOfMonth,.day,.hour,.minute,.second]  
// Cannot add in .nanosecond here (⬆︎) as Swift 4.1 does not consider nanoseconds a calendrical unit

dateComponentsFormatter.maximumUnitCount = 1
dateComponentsFormatter.unitsStyle = .full
dateComponentsFormatter.string(from: Date(), to: Date(timeIntervalSinceNow: 4000000))  // "1 month"

---

let date1 = DateComponents(calendar: .current, year: 2014, month: 11, day: 28, hour: 5, minute: 9).date!
let date2 = DateComponents(calendar: .current, year: 2015, month: 8, day: 28, hour: 5, minute: 9).date!

let years = date2.years(from: date1)             // 0
let months = date2.months(from: date1)           // 9
let weeks = date2.weeks(from: date1)             // 39
let days = date2.days(from: date1)               // 273
let hours = date2.hours(from: date1)             // 6,553
let minutes = date2.minutes(from: date1)         // 393,180
let seconds = date2.seconds(from: date1)         // 23,590,800
let nanoseconds = date2.nanoseconds(from: date1) // 23,590,800,000,000,000

let timeOffset = date2.offset(from: date1) // "9M"

let date3 = DateComponents(calendar: .current, year: 2014, month: 11, day: 28, hour: 5, minute: 9).date!
let date4 = DateComponents(calendar: .current, year: 2015, month: 11, day: 28, hour: 5, minute: 9).date!

let timeOffset2 = date4.offset(from: date3) // "1y"

let date5 = DateComponents(calendar: .current, year: 2017, month: 4, day: 28).date!
let now = Date()
let timeOffset3 = now.offset(from: date5) // "1w"

#2

If someone would need to display all time units e.g "hours minutes seconds" not just "hours". Let's say the time difference between two dates is 1hour 59minutes 20seconds. This function will display "1h 59m 20s".

如果有人需要显示所有时间单位e。g“小时分秒”而不仅仅是“小时”。假设两次约会的时差是1小时59分20秒。此函数将显示“1h 59m 20s”。

Here is my code:

这是我的代码:

extension NSDate {

    func offsetFrom(date : NSDate) -> String {

        let dayHourMinuteSecond: NSCalendarUnit = [.Day, .Hour, .Minute, .Second]
        let difference = NSCalendar.currentCalendar().components(dayHourMinuteSecond, fromDate: date, toDate: self, options: [])

        let seconds = "\(difference.second)s"
        let minutes = "\(difference.minute)m" + " " + seconds
        let hours = "\(difference.hour)h" + " " + minutes
        let days = "\(difference.day)d" + " " + hours

        if difference.day    > 0 { return days }
        if difference.hour   > 0 { return hours }
        if difference.minute > 0 { return minutes }
        if difference.second > 0 { return seconds }
        return ""
    }

}

In Swift 3:

在斯威夫特3:

extension Date {

    func offsetFrom(date : Date) -> String {

        let dayHourMinuteSecond: Set<Calendar.Component> = [.day, .hour, .minute, .second]
        let difference = NSCalendar.current.dateComponents(dayHourMinuteSecond, from: date, to: self);

        let seconds = "\(difference.second ?? 0)s"
        let minutes = "\(difference.minute ?? 0)m" + " " + seconds
        let hours = "\(difference.hour ?? 0)h" + " " + minutes
        let days = "\(difference.day ?? 0)d" + " " + hours

        if let day = difference.day, day          > 0 { return days }
        if let hour = difference.hour, hour       > 0 { return hours }
        if let minute = difference.minute, minute > 0 { return minutes }
        if let second = difference.second, second > 0 { return seconds }
        return ""
    }

}

#3

You ask:

你问:

I'd like to have a function that compares the two dates and if(seconds > 60) then it returns minutes, if(minutes > 60) return hours and if(hours > 24) return days and so on.

我想要一个函数来比较这两个日期和if(秒> 60)然后它返回分钟，if(分钟> 60)返回小时以及if(小时> 24)返回天等等。

I'm assuming that you're trying to build a string representation of the elapsed time between two dates. Rather than writing your own code to do that, Apple already has a class designed to do precisely that. Namely, use DateComponentsFormatter, set allowedUnits to whatever values make sense to your app, set unitsStyle to whatever you want (e.g. .full), and then call string(from:to:).

我假设您正在构建两个日期之间经过时间的字符串表示形式。与其编写自己的代码来实现这一点，苹果已经有了一个专门用来实现这一点的类。也就是说，使用DateComponentsFormatter，将allowedUnits设置为对应用程序有意义的任何值，将unitsStyle设置为您想要的任何值(例如.full)，然后调用string(from:to:)。

E.g. in Swift 3:

例如在斯威夫特3:

let previousDate = ...
let now = Date()

let formatter = DateComponentsFormatter()
formatter.unitsStyle = .full
formatter.allowedUnits = [.month, .day, .hour, .minute, .second]
formatter.maximumUnitCount = 2   // often, you don't care about seconds if the elapsed time is in months, so you'll set max unit to whatever is appropriate in your case

let string = formatter.string(from: previousDate, to: now)

This also will localize the string appropriate for the device in question.

这也将本地化相应于相关设备的字符串。

Or, in Swift 2.3:

或者,在迅速2.3:

let previousDate = ...
let now = NSDate()

let formatter = NSDateComponentsFormatter()
formatter.unitsStyle = .Full
formatter.allowedUnits = [.Month, .Day, .Hour, .Minute, .Second]
formatter.maximumUnitCount = 2

let string = formatter.stringFromDate(previousDate, toDate: now)

---

If you're looking for the actual numeric values, just use dateComponents. E.g. in Swift 3:

如果要查找实际的数值，只需使用dateComponents。例如在斯威夫特3:

let components = Calendar.current.dateComponents([.month, .day, .hour, .minute, .second], from: previousDate, to: now)

Or, in Swift 2.3:

或者,在迅速2.3:

let components = NSCalendar.currentCalendar().components([.Month, .Day, .Hour, .Minute, .Second], fromDate: previousDate, toDate: now, options: [])

#4

   func dateDiff(dateStr:String) -> String {
            var f:NSDateFormatter = NSDateFormatter()
            f.timeZone = NSTimeZone.localTimeZone()
            f.dateFormat = "yyyy-M-dd'T'HH:mm:ss.SSSZZZ"

            var now = f.stringFromDate(NSDate())
            var startDate = f.dateFromString(dateStr)
            var endDate = f.dateFromString(now)
            var calendar: NSCalendar = NSCalendar.currentCalendar()

            let calendarUnits = NSCalendarUnit.CalendarUnitWeekOfMonth | NSCalendarUnit.CalendarUnitDay | NSCalendarUnit.CalendarUnitHour | NSCalendarUnit.CalendarUnitMinute | NSCalendarUnit.CalendarUnitSecond
            let dateComponents = calendar.components(calendarUnits, fromDate: startDate!, toDate: endDate!, options: nil)

            let weeks = abs(dateComponents.weekOfMonth)
            let days = abs(dateComponents.day)
            let hours = abs(dateComponents.hour)
            let min = abs(dateComponents.minute)
            let sec = abs(dateComponents.second)

            var timeAgo = ""

            if (sec > 0){
                if (sec > 1) {
                    timeAgo = "\(sec) Seconds Ago"
                } else {
                    timeAgo = "\(sec) Second Ago"
                }
            }

            if (min > 0){
                if (min > 1) {
                    timeAgo = "\(min) Minutes Ago"
                } else {
                    timeAgo = "\(min) Minute Ago"
                }
            }

            if(hours > 0){
                if (hours > 1) {
                    timeAgo = "\(hours) Hours Ago"
                } else {
                    timeAgo = "\(hours) Hour Ago"
                }
            }

            if (days > 0) {
                if (days > 1) {
                    timeAgo = "\(days) Days Ago"
                } else {
                    timeAgo = "\(days) Day Ago"
                }
            }

            if(weeks > 0){
                if (weeks > 1) {
                    timeAgo = "\(weeks) Weeks Ago"
                } else {
                    timeAgo = "\(weeks) Week Ago"
                }
            }

            print("timeAgo is===> \(timeAgo)")
            return timeAgo;
        }

#5

I added a "long" version to Leo Dabus's asnwer in case you want to have a string that says something like "2 weeks ago" instead of just "2w"...

我在Leo Dabus的asnwer上增加了一个“long”版本，以防您想要一个像“两周前”这样的字符串，而不是“2w”……

extension Date {
    /// Returns the amount of years from another date
    func years(from date: Date) -> Int {
        return Calendar.current.dateComponents([.year], from: date, to: self).year ?? 0
    }
    /// Returns the amount of months from another date
    func months(from date: Date) -> Int {
        return Calendar.current.dateComponents([.month], from: date, to: self).month ?? 0
    }
    /// Returns the amount of weeks from another date
    func weeks(from date: Date) -> Int {
        return Calendar.current.dateComponents([.weekOfYear], from: date, to: self).weekOfYear ?? 0
    }
    /// Returns the amount of days from another date
    func days(from date: Date) -> Int {
        return Calendar.current.dateComponents([.day], from: date, to: self).day ?? 0
    }
    /// Returns the amount of hours from another date
    func hours(from date: Date) -> Int {
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }
    /// Returns the amount of minutes from another date
    func minutes(from date: Date) -> Int {
        return Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
    }
    /// Returns the amount of seconds from another date
    func seconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.second], from: date, to: self).second ?? 0
    }
    /// Returns the a custom time interval description from another date
    func offset(from date: Date) -> String {
        if years(from: date)   > 0 { return "\(years(from: date))y"   }
        if months(from: date)  > 0 { return "\(months(from: date))M"  }
        if weeks(from: date)   > 0 { return "\(weeks(from: date))w"   }
        if days(from: date)    > 0 { return "\(days(from: date))d"    }
        if hours(from: date)   > 0 { return "\(hours(from: date))h"   }
        if minutes(from: date) > 0 { return "\(minutes(from: date))m" }
        if seconds(from: date) > 0 { return "\(seconds(from: date))s" }
        return ""
    }

    func offsetLong(from date: Date) -> String {
        if years(from: date)   > 0 { return years(from: date) > 1 ? "\(years(from: date)) years ago" : "\(years(from: date)) year ago" }
        if months(from: date)  > 0 { return months(from: date) > 1 ? "\(months(from: date)) months ago" : "\(months(from: date)) month ago" }
        if weeks(from: date)   > 0 { return weeks(from: date) > 1 ? "\(weeks(from: date)) weeks ago" : "\(weeks(from: date)) week ago"   }
        if days(from: date)    > 0 { return days(from: date) > 1 ? "\(days(from: date)) days ago" : "\(days(from: date)) day ago" }
        if hours(from: date)   > 0 { return hours(from: date) > 1 ? "\(hours(from: date)) hours ago" : "\(hours(from: date)) hour ago"   }
        if minutes(from: date) > 0 { return minutes(from: date) > 1 ? "\(minutes(from: date)) minutes ago" : "\(minutes(from: date)) minute ago" }
        if seconds(from: date) > 0 { return seconds(from: date) > 1 ? "\(seconds(from: date)) seconds ago" : "\(seconds(from: date)) second ago" }
        return ""
    }

}

#6

combined Extension + DateComponentsFormatter from the answer of @leo-dabus

将扩展+ DateComponentsFormatter从@leo-dabus的答案中分离出来。

Xcode 8.3 • Swift 3.1

Xcode 8.3•Swift 3.1

extension DateComponentsFormatter {
    func difference(from fromDate: Date, to toDate: Date) -> String? {
        self.allowedUnits = [.year,.month,.weekOfMonth,.day]
        self.maximumUnitCount = 1
        self.unitsStyle = .full
        return self.string(from: fromDate, to: toDate)
    }
}

let dateComponentsFormatter = DateComponentsFormatter()
dateComponentsFormatter.difference(from: Date(), to: Date(timeIntervalSinceNow: 4000000)) // "1 month"

#7

Slightly modified code for Swift 3.0

对Swift 3.0稍微做了修改

let calendar = NSCalendar.current as NSCalendar

// Replace the hour (time) of both dates with 00:00
let date1 = calendar.startOfDay(for: startDateTime)
let date2 = calendar.startOfDay(for: endDateTime)

let flags = NSCalendar.Unit.day
let components = calendar.components(flags, from: date1, to: date2, options: [])

return components.day!

#8

With Swift 3, according to your needs, you may choose one of the two following ways to solve your problem.

使用Swift 3，根据您的需要，您可以选择以下两种方式之一来解决您的问题。

---

1. Display the difference between two dates to the user

You can use a DateComponentsFormatter to create strings for your app’s interface. DateComponentsFormatter has a maximumUnitCount property with the following declaration:

您可以使用DateComponentsFormatter为应用程序的接口创建字符串。DateComponentsFormatter具有maximumUnitCount属性，其声明如下:

var maximumUnitCount: Int { get set }

Use this property to limit the number of units displayed in the resulting string. For example, with this property set to 2, instead of “1h 10m, 30s”, the resulting string would be “1h 10m”. Use this property when you are constrained for space or want to round up values to the nearest large unit.

使用此属性来限制结果字符串中显示的单元数。例如，将此属性设置为2，而不是“1h 10m, 30s”，得到的字符串将是“1h 10m”。当您受空间限制或希望将值四舍五入到最近的大型单元时，请使用此属性。

By setting maximumUnitCount's value to 1, you are guaranteed to display the difference in only one DateComponentsFormatter's unit (years, months, days, hours or minutes).

通过将maximumUnitCount的值设置为1，您可以保证只在一个DateComponentsFormatter的单元(年、月、日、小时或分钟)中显示差异。

The Playground code below shows how to display the difference between two dates:

下面的操场代码展示了如何显示两个日期之间的差异:

import Foundation

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

let dateComponentsFormatter = DateComponentsFormatter()
dateComponentsFormatter.allowedUnits = [NSCalendar.Unit.year, .month, .day, .hour, .minute]
dateComponentsFormatter.maximumUnitCount = 1
dateComponentsFormatter.unitsStyle = DateComponentsFormatter.UnitsStyle.full
let timeDifference = dateComponentsFormatter.string(from: oldDate, to: newDate)

print(String(reflecting: timeDifference)) // prints Optional("5 hours")

Note that DateComponentsFormatter rounds up the result. Therefore, a difference of 4 hours and 30 minutes will be displayed as 5 hours.

注意，DateComponentsFormatter充实了结果。因此，4小时30分钟的差异将显示为5小时。

If you need to repeat this operation, you can refactor your code:

如果需要重复此操作，可以重构代码:

import Foundation

struct Formatters {

    static let dateComponentsFormatter: DateComponentsFormatter = {
        let dateComponentsFormatter = DateComponentsFormatter()
        dateComponentsFormatter.allowedUnits = [NSCalendar.Unit.year, .month, .day, .hour, .minute]
        dateComponentsFormatter.maximumUnitCount = 1
        dateComponentsFormatter.unitsStyle = DateComponentsFormatter.UnitsStyle.full
        return dateComponentsFormatter
    }()

}

extension Date {

    func offset(from: Date) -> String? {
        return Formatters.dateComponentsFormatter.string(from: oldDate, to: self)
    }

}

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

let timeDifference = newDate.offset(from: oldDate)
print(String(reflecting: timeDifference)) // prints Optional("5 hours")

---

2. Get the difference between two dates without formatting

If you don't need to display with formatting the difference between two dates to the user, you can use Calendar. Calendar has a method dateComponents(_:from:to:) that has the following declaration:

如果不需要将两个日期之间的差异格式化显示给用户，可以使用Calendar。Calendar有一个方法dateComponents(_:from:to:)，该方法具有以下声明:

func dateComponents(_ components: Set<Calendar.Component>, from start: Date, to end: Date) -> DateComponents

Returns the difference between two dates.

返回两个日期之间的差值。

The Playground code below that uses dateComponents(_:from:to:) shows how to retrieve the difference between two dates by returning the difference in only one type of Calendar.Component (years, months, days, hours or minutes).

下面的操场代码使用了dateComponents(_:from:to:)展示了如何通过只返回一个日历类型的差异来检索两个日期之间的差异。组成部分(年、月、日、小时或分钟)。

import Foundation

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

let descendingOrderedComponents = [Calendar.Component.year, .month, .day, .hour, .minute]
let dateComponents = Calendar.current.dateComponents(Set(descendingOrderedComponents), from: oldDate, to: newDate)
let arrayOfTuples = descendingOrderedComponents.map { ($0, dateComponents.value(for: $0)) }

for (component, value) in arrayOfTuples {
    if let value = value, value > 0 {
        print(component, value) // prints hour 4
        break
    }
}

If you need to repeat this operation, you can refactor your code:

如果需要重复此操作，可以重构代码:

import Foundation

extension Date {

    func offset(from: Date) -> (Calendar.Component, Int)? {
        let descendingOrderedComponents = [Calendar.Component.year, .month, .day, .hour, .minute]
        let dateComponents = Calendar.current.dateComponents(Set(descendingOrderedComponents), from: from, to: self)
        let arrayOfTuples = descendingOrderedComponents.map { ($0, dateComponents.value(for: $0)) }

        for (component, value) in arrayOfTuples {
            if let value = value, value > 0 {
                return (component, value)
            }
        }

        return nil
    }

}

let oldDate = Date(timeIntervalSinceReferenceDate: -16200)
let newDate = Date(timeIntervalSinceReferenceDate: 0)

if let (component, value) = newDate.offset(from: oldDate) {
    print(component, value) // prints hour 4
}

#9

In Swift 2.2

在斯威夫特2.2

    /// Returns the amount of years from another date
func years(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Year], fromDate: fromdate, toDate: NSDate(), options: []).year ?? 0
}
/// Returns the amount of months from another date
func months(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Month], fromDate: fromdate, toDate: NSDate(), options: []).month ?? 0
}
/// Returns the amount of weeks from another date
func weeks(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.WeekOfYear], fromDate: fromdate, toDate: NSDate(), options: []).weekOfYear ?? 0
}
/// Returns the amount of days from another date
func days(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Day], fromDate: fromdate, toDate: NSDate(), options: []).day ?? 0
}
/// Returns the amount of hours from another date
func hours(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Hour], fromDate: fromdate, toDate: NSDate(), options: []).hour ?? 0
}
/// Returns the amount of minutes from another date
func minutes(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components([.Minute], fromDate: fromdate, toDate: NSDate(), options: []).minute ?? 0
}
/// Returns the amount of seconds from another date
func seconds(fromdate: NSDate) -> Int {
    return NSCalendar.currentCalendar().components(.Second, fromDate: fromdate, toDate: NSDate(), options: []).second ?? 0
}

#10

Here is my answer for the Swift 3 answers above. This is current as of Nov 2016, Xcode release was 8.2 Beta (8C23). Used some of both Sagar and Emin suggestions above and sometimes had to let Xcode autocomplete to suggest the syntax. It seemed like the syntax really changed to this beta version. buyDate I got from a DatePicker:

以下是我对上面快速回答3的回答。截至2016年11月，Xcode发布为8.2 Beta (8C23)。使用了上面提到的Sagar和Emin建议，有时还必须让Xcode自动完成以建议语法。看起来这个测试版本的语法真的变了。购买日期:

let calendar = NSCalendar.current as NSCalendar
let currentDate = Date()
let date1 = calendar.startOfDay(for: buyDate!)
let date2 = calendar.startOfDay(for: currentDate)      
let flags = NSCalendar.Unit.day
let components = calendar.components(flags, from: date1, to: date2)
NSLog(" day= \(components.day)")

#11

A small addition to Leo Dabus' answer to provide the plural versions and be more human readable.

利奥·达布斯的回答中增加了一个小部分，可以提供复数形式，使人更容易读懂。

Swift 3

斯威夫特3

extension Date {
    /// Returns the amount of years from another date
    func years(from date: Date) -> Int {
        return Calendar.current.dateComponents([.year], from: date, to: self).year ?? 0
    }
    /// Returns the amount of months from another date
    func months(from date: Date) -> Int {
        return Calendar.current.dateComponents([.month], from: date, to: self).month ?? 0
    }
    /// Returns the amount of weeks from another date
    func weeks(from date: Date) -> Int {
        return Calendar.current.dateComponents([.weekOfMonth], from: date, to: self).weekOfMonth ?? 0
    }
    /// Returns the amount of days from another date
    func days(from date: Date) -> Int {
        return Calendar.current.dateComponents([.day], from: date, to: self).day ?? 0
    }
    /// Returns the amount of hours from another date
    func hours(from date: Date) -> Int {
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }
    /// Returns the amount of minutes from another date
    func minutes(from date: Date) -> Int {
        return Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
    }
    /// Returns the amount of seconds from another date
    func seconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.second], from: date, to: self).second ?? 0
    }
    /// Returns the a custom time interval description from another date
    func offset(from date: Date) -> String {
        if years(from: date)   == 1 { return "\(years(from: date)) year"   } else if years(from: date)   > 1 { return "\(years(from: date)) years"   }
        if months(from: date)  == 1 { return "\(months(from: date)) month"  } else if months(from: date)  > 1 { return "\(months(from: date)) month"  }
        if weeks(from: date)   == 1 { return "\(weeks(from: date)) week"   } else if weeks(from: date)   > 1 { return "\(weeks(from: date)) weeks"   }
        if days(from: date)    == 1 { return "\(days(from: date)) day"    } else if days(from: date)    > 1 { return "\(days(from: date)) days"    }
        if hours(from: date)   == 1 { return "\(hours(from: date)) hour"   } else if hours(from: date)   > 1 { return "\(hours(from: date)) hours"   }
        if minutes(from: date) == 1 { return "\(minutes(from: date)) minute" } else if minutes(from: date) > 1 { return "\(minutes(from: date)) minutes" }
        return ""
    }
}

#12

If your purpose is to get the exact day number between two dates, you can work around this issue like this:

如果你的目的是在两个日期之间得到确切的日期，你可以这样处理这个问题:

// Assuming that firstDate and secondDate are defined
// ...

var calendar: NSCalendar = NSCalendar.currentCalendar()

// Replace the hour (time) of both dates with 00:00
let date1 = calendar.startOfDayForDate(firstDate)
let date2 = calendar.startOfDayForDate(secondDate)

let flags = NSCalendarUnit.DayCalendarUnit
let components = calendar.components(flags, fromDate: date1, toDate: date2, options: nil)

components.day  // This will return the number of day(s) between dates

#13

This is the shorter version: Basically I try to get the difference between the post timestamp with the Date() now.

这是较短的版本:基本上，我尝试获得post时间戳与Date()之间的差异。

// MARK: - UPDATE Time Stamp
static func updateTimeStampPost(postTimeStamp: Date?, _ completion: (_ finalString: String?) -> Void) {
    // date in the current state
    let date = Date()
    let dateComponentFormatter = DateComponentsFormatter()

    // change the styling date, wether second minute or hour
    dateComponentFormatter.unitsStyle = .abbreviated
    dateComponentFormatter.allowedUnits = [.second, .minute, .hour, .day, .weekOfMonth]
    dateComponentFormatter.maximumUnitCount = 1

    // return the date new format as a string in the completion
    completion(dateComponentFormatter.string(from: postTimeStamp!, to: date))
}

#14

For XCode Version 8.3.3 & Swift 3.0:

对于XCode版本8.3.3和Swift 3.0:

    let dateFormatter = DateFormatter()
    dateFormatter.dateStyle = .medium
    dateFormatter.timeStyle = .short

    var beginDate = "2017-08-24 12:00:00"
    var endDate = "2017-09-07 12:00:00"


    let startDateTime = dateFormatter.date(from: beginDate) //according to date format your date string
    print(startDateTime ?? "") //Convert String to Date

    let endDateTime = dateFormatter.date(from: endDate) //according to date format your date string
    print(endDateTime ?? "") //Convert String to Date

    let dateComponentsFormatter = DateComponentsFormatter()
    dateComponentsFormatter.allowedUnits = [NSCalendar.Unit.minute,NSCalendar.Unit.hour,NSCalendar.Unit.day]


   let interval = endDateTime!.timeIntervalSince(startDateTime!)
   var diff = dateComponentsFormatter.string(from: interval)!

   print(diff)

   var day_i  = 0
   var hour_i = 0
   var min_i = 0


     if (diff.contains("d"))
       {
              let day = diff.substring(to: (diff.range(of: "d")?.lowerBound)!)

               day_i  = Int(day)!
               print ("day --> \(day_i)")

               diff = diff.substring(from:(diff.range(of : " ")?.upperBound )!)
               print(diff)
       }


       let hour = diff.substring(to: (diff.range(of : ":")?.lowerBound )!)
       hour_i  = Int(hour)!
       print ("hour --> \(hour_i)")

       let min = diff.substring(from: (diff.range(of : ":")?.upperBound )!)
       min_i  = Int(min)!
       print ("min --> \(min_i)")