swift当月的第一天和最后一天

问题描述 投票：51回答：8

我试图迅速获得本月的第一天和最后一天。

到目前为止，我有以下内容：

let dateFormatter = NSDateFormatter()
let date = NSDate()
dateFormatter.dateFormat = "yyyy-MM-dd"
let calendar = NSCalendar.currentCalendar()
let components = calendar.components([.Year, .Month, .Day, .Hour, .Minute, .Second], fromDate: date)

let month = components.month
let year = components.year

let startOfMonth = ("\(year)-\(month)-01")

但我不知道如何获得最后的约会。有缺点的内置方法吗？显然它必须考虑到闰年等。

ios swift nsdate nscalendar
8个回答
63
投票

你只需要一个月的第一天

let components = calendar.components([.Year, .Month], fromDate: date)
let startOfMonth = calendar.dateFromComponents(components)!
print(dateFormatter.stringFromDate(startOfMonth)) // 2015-11-01

要获取该月的最后一天，请添加一个月并减去一天：

let comps2 = NSDateComponents()
comps2.month = 1
comps2.day = -1
let endOfMonth = calendar.dateByAddingComponents(comps2, toDate: startOfMonth, options: [])!
print(dateFormatter.stringFromDate(endOfMonth)) // 2015-11-30

或者，使用rangeOfUnit方法，它为您提供月份的开始和长度：

var startOfMonth : NSDate?
var lengthOfMonth : NSTimeInterval = 0
calendar.rangeOfUnit(.Month, startDate: &startOfMonth, interval: &lengthOfMonth, forDate: date)

对于月份最后一天的日期，请添加月份减去一秒的长度：

let endOfMonth = startOfMonth!.dateByAddingTimeInterval(lengthOfMonth - 1)
103
投票

Swift 3和4 drop-in扩展

使用Swift 3+，这实际上变得更加容易：

  1. 你可以毫无保护地做到这一点（如果你愿意，你可以这样做，但因为DateComponents现在是非可选类型，所以不再需要）。
  2. 使用iOS 8的startOfDayForDate（现在是startOfDay），您不需要手动将时间设置为12pm，除非您在跨时区进行一些非常疯狂的日历计算。

值得一提的是，其他一些答案声称你可以通过使用Calendar.current.date(byAdding: .month, value: 0, to: Date())!来快速解决这个问题，但是如果失败了，那就是它实际上并没有将当天归零，或者说明了时区的差异。

干得好：

extension Date {
    func startOfMonth() -> Date {
        return Calendar.current.date(from: Calendar.current.dateComponents([.year, .month], from: Calendar.current.startOfDay(for: self)))!
    }

    func endOfMonth() -> Date {
        return Calendar.current.date(byAdding: DateComponents(month: 1, day: -1), to: self.startOfMonth())!
    }
}

print(Date().startOfMonth())     // "2018-02-01 08:00:00 +0000\n"
print(Date().endOfMonth())       // "2018-02-28 08:00:00 +0000\n"
25
投票

使用Swift 3和iOS 10，我发现这样做最简单的方法是Calendar的dateInterval(of:for:)：

guard let interval = calendar.dateInterval(of: .month, for: Date()) else { return }

然后，您可以使用interval.start和interval.end来获取所需的日期。

19
投票

斯威夫特3

许多日期示例：

过去6个月，过去3个月，昨天，过去7天，过去30天，上个月，当前月份开始和结束，上个月开始和结束日期

let startDate = dateFormatter.string(from: Date().getThisMonthStart()!)
let endDate = dateFormatter.string(from: Date().getThisMonthEnd()!)

extension Date {

func getLast6Month() -> Date? {
    return Calendar.current.date(byAdding: .month, value: -6, to: self)
}

func getLast3Month() -> Date? {
    return Calendar.current.date(byAdding: .month, value: -3, to: self)
}

func getYesterday() -> Date? {
    return Calendar.current.date(byAdding: .day, value: -1, to: self)
}

func getLast7Day() -> Date? {
    return Calendar.current.date(byAdding: .day, value: -7, to: self)
}
func getLast30Day() -> Date? {
    return Calendar.current.date(byAdding: .day, value: -30, to: self)
}

func getPreviousMonth() -> Date? {
    return Calendar.current.date(byAdding: .month, value: -1, to: self)
}

// This Month Start
func getThisMonthStart() -> Date? {
    let components = Calendar.current.dateComponents([.year, .month], from: self)
    return Calendar.current.date(from: components)!
}

func getThisMonthEnd() -> Date? {
    let components:NSDateComponents = Calendar.current.dateComponents([.year, .month], from: self) as NSDateComponents
    components.month += 1
    components.day = 1
    components.day -= 1
    return Calendar.current.date(from: components as DateComponents)!
}

//Last Month Start
func getLastMonthStart() -> Date? {
    let components:NSDateComponents = Calendar.current.dateComponents([.year, .month], from: self) as NSDateComponents
    components.month -= 1
    return Calendar.current.date(from: components as DateComponents)!
}

//Last Month End
func getLastMonthEnd() -> Date? {
    let components:NSDateComponents = Calendar.current.dateComponents([.year, .month], from: self) as NSDateComponents
    components.day = 1
    components.day -= 1
    return Calendar.current.date(from: components as DateComponents)!
}

}
5
投票

2017...

首先，获得您需要的月份：

    let cal = Calendar.current
    let d = Calendar.current.date(byAdding: .month, value: 0, to: Date())!

    // for "last month" just use -1, for "next month" just use 1, etc

要获得每月第一天的星期几：

    let c = cal.dateComponents([.year, .month], from: d)
    let FDOM = cal.date(from: c)!
    let dowFDOM = cal.component(.weekday, from: FDOM)

    print("the day-of-week on the 1st is ... \(dowFDOM)")
    // so, that's 1=Sunday, 2=Monday, etc.

要获得当月的天数：

    let r = cal.range(of: .day, in: .month, for: d)!
    let kDays = r.count

    print("the number of days is ... \(kDays)")
4
投票

斯威夫特4

如果您只需要序数日：

func lastDay(ofMonth m: Int, year y: Int) -> Int {
    let cal = Calendar.current
    var comps = DateComponents(calendar: cal, year: y, month: m)
    comps.setValue(m + 1, for: .month)
    comps.setValue(0, for: .day)
    let date = cal.date(from: comps)!
    return cal.component(.day, from: date)
}

lastDay(ofMonth: 2, year: 2018)  // 28
lastDay(ofMonth: 2, year: 2020)  // 29
2
投票

使用Swift 3，您可以选择以下两种模式之一，以便检索一个月的第一天和最后一天。

#1. Using Calendar dateComponents(_:from:), date(from:) and date(byAdding:to:wrappingComponents:) methods

使用此模式，您首先获得一个月的第一天的日期，然后添加一个月并从中删除一天以获取该月的最后一天的日期。下面的Playground代码显示了如何设置它：

import Foundation

// Set calendar and date 
let calendar = Calendar.current
let date = calendar.date(byAdding: DateComponents(day: -10), to: Date())!

// Get first day of month
let firstDayComponents = calendar.dateComponents([.year, .month], from: date)
let firstDay = calendar.date(from: firstDayComponents)!

// Get last day of month
let lastDayComponents = DateComponents(month: 1, day: -1)
let lastDay = calendar.date(byAdding: lastDayComponents, to: firstDay)!

// Set date formatter
let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_UK")
dateFormatter.dateStyle = .long
dateFormatter.timeStyle = .long

// Print results
print(dateFormatter.string(from: date)) // Prints: 22 March 2017 at 18:07:15 CET
print(dateFormatter.string(from: firstDay)) // Prints: 1 March 2017 at 00:00:00 CET
print(dateFormatter.string(from: lastDay)) // Prints: 31 March 2017 at 00:00:00 CEST

#2. Using Calendar range(of:in:for:), dateComponents(_:from:) and date(from:) and methods

使用此模式，您可以在一个月内获得一系列绝对日值，然后从中检索该月的第一天和最后一天的日期。下面的Playground代码显示了如何设置它：

import Foundation

// Set calendar and date
let calendar = Calendar.current
let date = calendar.date(byAdding: DateComponents(day: -10), to: Date())!

// Get range of days in month
let range = calendar.range(of: .day, in: .month, for: date)! // Range(1..<32)

// Get first day of month
var firstDayComponents = calendar.dateComponents([.year, .month], from: date)
firstDayComponents.day = range.lowerBound
let firstDay = calendar.date(from: firstDayComponents)!

// Get last day of month
var lastDayComponents = calendar.dateComponents([.year, .month], from: date)
lastDayComponents.day = range.upperBound - 1
//lastDayComponents.day = range.count // also works
let lastDay = calendar.date(from: lastDayComponents)!

// Set date formatter
let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_UK")
dateFormatter.dateStyle = .long
dateFormatter.timeStyle = .long

// Print results
print(dateFormatter.string(from: date)) // prints: 22 March 2017 at 18:07:15 CET
print(dateFormatter.string(from: firstDay)) // prints: 1 March 2017 at 00:00:00 CET
print(dateFormatter.string(from: lastDay)) // prints: 31 March 2017 at 00:00:00 CEST
2
投票

在swift 3中，如果你把0天组件放在一起，你可以得到这个月的最后一天。有一个示例代码：

 public func isMoreDays(date: Date, asc: Bool)->Bool{
    //components
    var dayComponents = self.getDateComponents(date: date)
    //asc is true if ascendant or false if descendant
    dayComponents.day = asc ?  0 : 1
    //plus 1 to month 'cos if you set up day to 0 you are going to the previous month
    dayComponents.month = asc ? dayComponents.month! + 1 : dayComponents.month

    //instantiate calendar and get the date
    let calendar : Calendar = NSCalendar.current
    let day = calendar.date(from: dayComponents)

    //date comparison
    if(day?.compare(date) == .orderedSame){
        return false
    }
    return true
}
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