Truncate NSDate (Zero-out time)

问题:

I want to generate a new NSDate with 0 hours, 0 minutes, and 0 seconds for time. The source date can be any random NSDate.

Is there a way to achieve this? The documentation did not help me with this.

---

Example

Have: 2010-10-30 10:14:13 GMT

Want: 2010-10-30 00:00:00 GMT

回答1:

unsigned int flags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay;
NSCalendar* calendar = [NSCalendar currentCalendar];
NSDateComponents* components = [calendar components:flags fromDate:date];
NSDate* dateOnly = [calendar dateFromComponents:components];

date is the date you want to remove the time from.

This separates the date and time and creates a new date with the default time (00:00:00).

EDIT

To take time zone into account:

NSDate* dateOnly = [[calendar dateFromComponents:components] dateByAddingTimeInterval:[[NSTimeZone localTimeZone]secondsFromGMT]];

回答2:

Use NSCalendar's rangeOfUnit:startDate:interval:forDate:. This code will choose the day boundary based on the current time zone. If you want a particular time zone, you need to create an NSCalendar and set its time zone appropriately.

- (NSDate*)boundaryForCalendarUnit:(NSCalendarUnit)calendarUnit
{
    NSDate *boundary;
    [[NSCalendar currentCalendar] rangeOfUnit:calendarUnit startDate:&boundary interval:NULL forDate:self];
    return boundary;
}

- (NSDate*)dayBoundary
{
    return [self boundaryForCalendarUnit:NSDayCalendarUnit];
}

回答3:

With Swift 3, you can choose one of the four following patterns in order to solve your problem.

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#1. Using Calendar startOfDay(for:)

startOfDay(for:) has the following declaration:

func startOfDay(for date: Date) -> Date

Returns the first moment of a given Date, as a Date.

The Playground code below shows how to use this method:

import Foundation

let date = Date()

// Get new date
let calendar = Calendar.current
let newDate = calendar.startOfDay(for: date)

// Format dates
let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_UK")
dateFormatter.dateStyle = .short
dateFormatter.timeStyle = .long

let formattedDate = dateFormatter.string(from: date)
let formattedNewDate = dateFormatter.string(from: newDate)

// Print formatted dates
print(formattedDate) // Prints: 30/03/2017, 15:14:41 CEST
print(formattedNewDate) // Prints: 30/03/2017, 00:00:00 CEST

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#2. Using Calendar date(bySettingHour:minute:second:of:matchingPolicy:repeatedTimePolicy:direction:)

date(bySettingHour:minute:second:of:matchingPolicy:repeatedTimePolicy:direction:) has the following declaration:

func date(bySettingHour hour: Int, minute: Int, second: Int, of date: Date, matchingPolicy: Calendar.MatchingPolicy = default, repeatedTimePolicy: Calendar.RepeatedTimePolicy = default, direction: Calendar.SearchDirection = default) -> Date?

Returns a new Date representing the date calculated by setting hour, minute, and second to a given time on a specified Date.

The Playground code below shows how to use this method:

import Foundation

let date = Date()

// Get new date
let calendar = Calendar.current
let newDate = calendar.date(bySettingHour: 0, minute: 0, second: 0, of: date)

// Format dates
let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_UK")
dateFormatter.dateStyle = .short
dateFormatter.timeStyle = .long

let formattedDate = dateFormatter.string(from: date)
let formattedNewDate = dateFormatter.string(from: newDate!)

// Print formatted dates
print(formattedDate) // Prints: 30/03/2017, 15:14:41 CEST
print(formattedNewDate) // Prints: 30/03/2017, 00:00:00 CEST

---

#3. Using Calendar dateComponents(_:from:) and date(from:) methods

dateComponents(_:from:) has the following declaration:

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

Returns all the date components of a date, using the calendar time zone.

date(from:) has the following declaration:

func date(from components: DateComponents) -> Date?

Returns a date created from the specified components.

The Playground code below shows how to use those methods:

import Foundation

let date = Date()

// Get new date
let calendar = Calendar.current
let components = calendar.dateComponents([.day, .month, .year], from: date)
let newDate = calendar.date(from: components)

// Format dates
let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_UK")
dateFormatter.dateStyle = .short
dateFormatter.timeStyle = .long

let formattedDate = dateFormatter.string(from: date)
let formattedNewDate = dateFormatter.string(from: newDate!)

// Print formatted dates
print(formattedDate) // Prints: 30/03/2017, 15:14:41 CEST
print(formattedNewDate) // Prints: 30/03/2017, 00:00:00 CEST

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#4. Using NSCalendar range(of:start:interval:for:)

range(of:start:interval:for:) has the following declaration:

func range(of unit: NSCalendar.Unit, start datep: AutoreleasingUnsafeMutablePointer<NSDate?>?, interval tip: UnsafeMutablePointer<TimeInterval>?, for date: Date) -> Bool

Returns by reference the starting time and duration of a given calendar unit that contains a given date.

The Playground code below shows how to use this method:

import Foundation

let date = Date()

// Get new date
let calendar = Calendar.current as NSCalendar
var newDate: NSDate?
calendar.range(of: .day, start: &newDate, interval: nil, for: date)

// Format dates
let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_UK")
dateFormatter.dateStyle = .short
dateFormatter.timeStyle = .long

let formattedDate = dateFormatter.string(from: date)
let formattedNewDate = dateFormatter.string(from: newDate as! Date)

// Print formatted dates
print(formattedDate) // Prints: 30/03/2017, 15:14:41 CEST
print(formattedNewDate) // Prints: 30/03/2017, 00:00:00 CEST

回答4:

I know its late, but there are now better methods: why dont you just use

Swift 2

NSCalendar.currentCalendar().dateBySettingHour(0, minute: 0, second: 0, ofDate: yourDateToZeroOutTime, options: [])

Swift 3 would be something without the NS prefix ;)

回答5:

Swift 3

extension Date {
    func trimTime() -> Date {
        var boundary = Date()
        var interval: TimeInterval = 0
        _ = Calendar.current.dateInterval(of: .day, start: &boundary, interval: &interval, for: self)

        return Date(timeInterval: TimeInterval(NSTimeZone.system.secondsFromGMT()), since: boundary)
    }
}

回答6:

I would use the description method to get the given date as a string, then modify the string and create your new date with initWithString.

initWithString: Returns an NSDate object initialized with a date and time value specified by a given string in the international string representation format.

• (id)initWithString:(NSString *)description Parameters description A string that specifies a date and time value in the international string representation format—YYYY-MM-DD HH:MM:SS ±HHMM, where ±HHMM is a time zone offset in hours and minutes from GMT (for example, “2001-03-24 10:45:32 +0600”). You must specify all fields of the format string, including the time zone offset, which must have a plus or minus sign prefix. Return Value An NSDate object initialized with a date and time value specified by aString.