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How do I find the beginning of the week from an NSDate?
(7 answers)
Closed 4 years ago.
If current date is 3 August 2018 (friday), i want to get 4 & 5 august 2018 (saturday and sunday)
if current date is 4 august (saturday), I still want to get 4 & 5 august 2018 (saturday and sunday)
if current date is 6 august (monday) then I want to get 11 & 12 August (saturday and sunday)
how to do that in swift?
Calendar has convenience methods for that
dateIntervalOfWeekend(containing:start:interval:) checks if the given date is in a weekend and returns the startDate and interval(duration in seconds) in the inout parameters. The Bool return value is true if the given date is within a weekend.
nextWeekend(startingAfter:start:interval:) returns startDate und interval in the inout parameters for the upcoming (.forward parameter) or passed (.backward) weekend.
let now = Date()
var startDate = Date()
var interval : TimeInterval = 0.0
if !Calendar.current.dateIntervalOfWeekend(containing: now, start: &startDate, interval: &interval) {
Calendar.current.nextWeekend(startingAfter: now, start: &startDate, interval: &interval, direction: .forward)
}
print(startDate, startDate.addingTimeInterval(interval))
If you need start of Saturday and start of Sunday then replace the last line with
let endDate = startDate.addingTimeInterval(interval-1)
print(startDate, Calendar.current.startOfDay(for: endDate))
Alternatively – suggested by Martin R (thanks) – use dateIntervalOfWeekend(containing:) / nextWeekend(startingAfter:) which both return a DateInterval object containing start, end and duration
let now = Date()
let calendar = Calendar.current
let weekEndInterval = calendar.dateIntervalOfWeekend(containing: now) ?? calendar.nextWeekend(startingAfter: now)!
let startDate = weekEndInterval.start
let endDate = startDate.addingTimeInterval(weekEndInterval.duration-1)
print(startDate, calendar.startOfDay(for: endDate))
let (nextSaturday,orderTotal) = getWeekends()
print(nextSaturday)
print(nextSunday)
func getWeekends() -> (Date,Date) {
let today = Date()
let calendar = Calendar.current
let todayWeekday = calendar.component(.weekday, from: today)
let addWeekdays = 7 - todayWeekday
var components = DateComponents()
components.weekday = addWeekdays
let nextSaturday = calendar.date(byAdding: components, to: today)
components.weekday = addWeekdays + 1
let nextSunday = calendar.date(byAdding: components, to: today)
return (nextSaturday,nextSunday)
}
Related
How can I get the date of previous month matching specified day ? in Swift
if I have this function getPreviousMonthDate(matchingDay day: Int) -> Date
Examples:
following (dd/mm/yyyy)
If Today is 25/07/2022 and I call getPreviousMonthDate(matchingDay: 27)
: return value would be 27/06/2022 .
If Today is 18/04/2022 and I call getPreviousMonthDate(matchingDay: 14)
: return value would be 14/03/2022 .
If Today is 15/01/2022 and I call getPreviousMonthDate(matchingDay: 16)
: return value would be 16/12/2021 .
and so on...
You can use date components as following:
func getPreviousMonthDate(matchingDay day: Int) -> Date {
let calendar = Calendar.current
let comps = calendar.dateComponents([.year, .month, .day], from: Date())
var comps2 = DateComponents()
comps2.year = comps.year
comps2.month = comps.month! - 1
comps2.day = day
return calendar.date(from: comps2)!
}
I force-unwrapped the date to match your function declaration, I suggest that you deal with the optional dates properly though.
I am having a small issue with getting the total days in a month using Swift.
I have extended the Date class and created this function:
func daysInMonth() -> Int {
print(self.day) ##30
print(self.month) ##12
print(self) ## 2021-11-30 23:46:29 +0000
print(Calendar.current.range(of: .day, in: .month, for: self)?.count) ##31
return Calendar.current.range(of: .day, in: .month, for: self)?.count ?? 0
}
I have set the Date&Time to the 30th of November, at 11:45 PM in the settings of my Mac, in Preferences.
I called the above function at 11:46 PM and obtained the above results (inline, next to the print statements).
The date output is correct as well as the day. The month output is wrong and the result is 31 days in the month of November.
If I run this exact same code before 10:00 PM, I get the right result which is 30 days.
Does anyone know why this is happening?
Thank you,
Paprika
It's a GMT offset issue combined with the current day in a month.
When you create a date without set a day, it will be set to the first day of the month.
So, if your timezone offset is for example -4 means your are 4 hours behind the GMT 0 and by default the timezone defined at Calendar.current is equal the system timezone. So what it means? Means you'll obtain the previous month if you test it in a boundary of 23 + (-4) or the next month if your offset is positive.
You can test this behaviour copying'n paste the following code in the Playground.
func getDaysInMonth(month: Int, year: Int, offset: Int = 0) -> Int? {
let someDate = DateComponents(year: year, month: month, hour: 3)
var current = Calendar.current
let timezone = TimeZone(secondsFromGMT: 60 * 60 * offset)!
current.timeZone = timezone
guard let someDay = current.date(from: someDate) else { return nil }
print("date: \(someDay)") // this will always
return someDay.daysInCurrentMonth
}
for hour in -12...12 {
print("hour: \(hour)\ndays: \(getDaysInMonth(month: 10, year: 2021, offset: hour) ?? -1)")
print("---\n")
}
extension Date {
var daysInCurrentMonth: Int? {
Calendar.current.range(of: .day, in: .month, for: self)?.count
}
}
Notice the days will change starting by your current system time zone (notice only the month will change).
How to fix this?
In your case, I guess you just want to show how many days a month have, so you can just set the to zero like this:
TimeZone(secondsFromGMT: 0)
Do this change at a instance of Calendar.current and check if it works for you.
It appears there something wrong with your Date extension methods for .day and .month.
Without seeing code it's hard to determine what the problem is though. Below is some code for returning the current month (Int) and current numbered day of month (Int)
extension Date
{
var month: Int
{
let date = Date()
let calendar = Calendar.current
let components = calendar.dateComponents([.month], from: date)
return components.month
}
var day: Int
{
let date = Date()
let calendar = Calendar.current
let components = calendar.dateComponents([.day], from: self)
return components.day
}
}
Please also ensure your time/date settings are correct on your mac/simulator/device. If these are wrong - it could have been jumping to a different month if you were in a timezone that was ahead a few hours.
How to get the current date in unix-epoch?
timeIntervalSince1970 prints the current time. Is there any way to get today's time at 12 AM?
For example, The current time is : Jan 7, 2018 5:30 PM. timeIntervalSince1970 will print the current time i.e. 1546903800000.
Current date in epoch system will be Jan 7, 2018 00:00 AM. i.e 1546848000000
This can be done very simply using the following code. No need for date components or other complications.
var calendar = Calendar.current
// Use the following line if you want midnight UTC instead of local time
//calendar.timeZone = TimeZone(secondsFromGMT: 0)
let today = Date()
let midnight = calendar.startOfDay(for: today)
let tomorrow = calendar.date(byAdding: .day, value: 1, to: midnight)!
let midnightEpoch = midnight.timeIntervalSince1970
let tomorrowEpoch = tomorrow.timeIntervalSince1970
I would do this with components.
Assuming you need time in seconds as defined by time(2). If you need in milliseconds as defined by time(3), then you can multiply it out by 1000.
// Get right now as it's `DateComponents`.
let now = Calendar.current.dateComponents(in: .current, from: Date())
// Create the start of the day in `DateComponents` by leaving off the time.
let today = DateComponents(year: now.year, month: now.month, day: now.day)
let dateToday = Calendar.current.date(from: today)!
print(dateToday.timeIntervalSince1970)
// Add 1 to the day to get tomorrow.
// Don't worry about month and year wraps, the API handles that.
let tomorrow = DateComponents(year: now.year, month: now.month, day: now.day! + 1)
let dateTomorrow = Calendar.current.date(from: tomorrow)!
print(dateTomorrow.timeIntervalSince1970)
You can get yesterday by subtracting 1.
If you need this in the universal time (UTC, GMT, Z… whatever name you give universal time), then use the following.
let utc = TimeZone(abbreviation: "UTC")!
let now = Calendar.current.dateComponents(in: utc, from: Date())
Use this extension to get today's and tomorrow's date
extension Date {
static var tomorrow: Date { return Date().dayAfter }
static var today: Date {return Date()}
var dayAfter: Date {
return Calendar.current.date(byAdding: .day, value: 1, to: Date())!
}
}
Also try adding following code in date extension:
extension Date
{
var startOfDay: Date
{
return Calendar.current.startOfDay(for: self)
}
func getDate(dayDifference: Int) -> Date {
var components = DateComponents()
components.day = dayDifference
return Calendar.current.date(byAdding: components, to:startOfDay)!
}
}
You can use the following method to get any date by adding days or months or years
by specifying the Calendar Component and the increment value of this component:
func getSpecificDate(byAdding component: Calendar.Component, value: Int) -> Date {
let noon = Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: self)!
return Calendar.current.date(byAdding: component, value: value, to: noon)!
}
Where the component wil be one from the following option :
( .day , .month , .year ) and the value will be the amount you want to add for this component
for example to get the next year date you can use the following code:
var nextYear = getSpecificDate(byAdding: .year, value: 1).timeIntervalSince1970
I have two NSDate which are initiated from UTC dates.
Lets call them (A & B)
I know that the A represents a day in China and B represents a day in USA. (I know the time zones.) How can I calculate the difference in days between the two...?
I have been using the following method which is obviously incorrect.
class func daysDifferenceIn(firstDate: NSDate, firstTimeZone: String, secondDate: NSDate, secondTimeZone: String) -> Int {
objc_sync_enter(self)
let firstDateComponents = NSCalendar.CommonCalendar.componentsInTimeZone(NSTimeZone(name: firstTimeZone)!, fromDate: firstDate)
let secondDateComponents = NSCalendar.CommonCalendar.componentsInTimeZone(NSTimeZone(name: secondTimeZone)!, fromDate: secondDate)
NSCalendar.CommonCalendar.timeZone = NSTimeZone(name: firstTimeZone)!
let firstCalDate = NSCalendar.CommonCalendar.dateFromComponents(firstDateComponents)
NSCalendar.CommonCalendar.timeZone = NSTimeZone(name: secondTimeZone)!
let secondCalDate = NSCalendar.CommonCalendar.dateFromComponents(secondDateComponents)
objc_sync_exit(self)
return firstCalDate!.numberOfDaysUntilDateTime(secondCalDate!)
}
func numberOfDaysUntilDateTime(toDateTime: NSDate, inTimeZone timeZone: NSTimeZone? = nil) -> Int {
let calendar = NSCalendar.CommonCalendar
if let timeZone = timeZone {
calendar.timeZone = timeZone
}
var fromDate: NSDate?, toDate: NSDate?
calendar.rangeOfUnit(.Day, startDate: &fromDate, interval: nil, forDate: self)
calendar.rangeOfUnit(.Day, startDate: &toDate, interval: nil, forDate: toDateTime)
let difference = calendar.components(.Day, fromDate: fromDate!, toDate: toDate!, options: [])
return difference.day
}
I can manually subtract day components from firstDateComponents and secondDateComponents which I don't want to do as I have to look for edge cases of 31 and 28 and so on.
Any help is appreciated. Thanks.
UPDATE
First date is 2017-02-10 16:15:00 +0000
Second date is 2017-02-11 03:20:00 +0000 Both are UTC.
firstTimeZone String "Asia/Shanghai"
secondTimeZone String "America/Los_Angeles"
So the day difference is -1 Day. Basically I am implementing flight status and you can see the following link as the flight lands 1 day prior to take day. As it flies from West to East.
https://www.google.co.in/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=ua+890
Also a description of Date components.
Printing description of firstDateComponents:
<NSDateComponents: 0x600000142310>
Calendar: <CFCalendar 0x60000088b6d0 [0x10c5d3df0]>{identifier = 'gregorian'}
TimeZone: Asia/Shanghai (GMT+8) offset 28800
Era: 1
Calendar Year: 2017
Month: 2
Leap month: no
Day: 11
Hour: 0
Minute: 15
Second: 0
Nanosecond: 0
Quarter: 0
Year for Week of Year: 2017
Week of Year: 6
Week of Month: 2
Weekday: 7
Weekday Ordinal: 2
Printing description of secondDateComponents:
<NSDateComponents: 0x60000014b8f0>
Calendar: <CFCalendar 0x60000049b620 [0x10c5d3df0]>{identifier = 'gregorian'}
TimeZone: America/Los_Angeles (PST) offset -28800
Era: 1
Calendar Year: 2017
Month: 2
Leap month: no
Day: 10
Hour: 19
Minute: 20
Second: 0
Nanosecond: 0
Quarter: 0
Year for Week of Year: 2017
Week of Year: 6
Week of Month: 2
Weekday: 6
Weekday Ordinal: 2
This is an odd case. You're looking for the difference in calendar dates between two Dates when those dates are evaluated in a specific time zone.
I did some playing, and came up with code that works for dates that fall in the same year:
let date = Date()
guard let nycTimeZone = TimeZone(abbreviation: "EST"),
let nzTimeZone = TimeZone(abbreviation: "NZDT") else {
fatalError()
}
var nycCalendar = Calendar(identifier: .gregorian)
nycCalendar.timeZone = nycTimeZone
var nzCalendar = Calendar(identifier: .gregorian)
nzCalendar.timeZone = nzTimeZone
let now = Date()
let nycDayOfYear = nycCalendar.ordinality(of: .day, in: .year, for: now)
var nzDayOfYear = nzCalendar.ordinality(of: .day, in: .year, for: now)
I'm using New York and Aukland, NZ as my time zones because as of the time of this writing, those zones are on different dates.
As of now (~12:00 PM on Feb 11, 2017 in US Eastern Standard Time (UTC - 5) the code above gives
nycDayOfYear = 42
and
nzDayOfYear = 43
It would take some work to make that calculation work across year boundaries.
Curiously, the following code:
var nzDayOfEra = nzCalendar.ordinality(of: .day, in: .era, for: now)
let nycDayOfEra = nycCalendar.ordinality(of: .day, in: .era, for: now)
Gives the same value for both NZ and NYC. I'm not sure why.
EDIT:
Ok, I did some experimenting and got code that works. What I do is to convert both dates to month/day/year date components using a calendar set to the local time zone for each time. Then I use a method dateComponents(_:from:to:) to calculate the difference between those 2 DateComponents, in days:
import UIKit
let date = Date()
guard let nycTimeZone = TimeZone(abbreviation: "EST"),
let nzTimeZone = TimeZone(abbreviation: "NZDT") else {
fatalError()
}
var nycCalendar = Calendar(identifier: .gregorian)
nycCalendar.timeZone = nycTimeZone
var nzCalendar = Calendar(identifier: .gregorian)
nzCalendar.timeZone = nzTimeZone
let now = Date()
let nycDateComponents = nycCalendar.dateComponents([.month, .day, .year], from: now)
let nzDateComponents = nzCalendar.dateComponents([.month, .day, .year], from: now)
let difference = Calendar.current.dateComponents([.day],
from: nycDateComponents,
to: nzDateComponents)
let daysDifference = difference.days
As of this writing that gives a daysDifference of 1. Since we're using the dateComponents(_:from:to:) function, it takes care of the math to calculate the number of days difference between the 2 month/day/year DateComponents.
A NSDate represents a moment in time. It has no time zone. Only string representations of dates have time zone information.
If you have the dates, just take the number of days between them. Don't worry about time zones.
Usually:
let difference = calendar.components(.Day, fromDate: self, toDate: toDate!, options: [])
return difference.day
should be enough.
Have you tried using let interval = laterDate.timeIntervalSinceDate(earlierDate)? This will return the difference between the two dates in seconds.
I'm trying to return Monday 00:00 from my date. This is my code:
func getMonday(myDate: Date) -> Date {
let cal = Calendar.current
let comps = cal.dateComponents([.weekOfYear, .yearForWeekOfYear], from: myDate)
let beginningOfWeek = cal.date(from: comps)!
return beginningOfWeek
}
My problem is that it does not return Monday 00:00 , but Saturday 22:00.
Example:
let monday1 = getMonday(myDate: date) //date is: 2016-10-04 17:00:00
print(monday1) //Prints: 2016-10-01 22:00:00 (Saturday)
My question is:
How to return Monday 00:00 from myDate?
Thank you very much.
Your code returns the first day in the given week, that may be
a Sunday or Monday (or perhaps some other day), depending on your locale.
If you want Monday considered to be the first weekday then set
cal.firstWeekday = 2
If you want the Monday of the given week, independent of what the
start of the week is, then set comps.weekday = 2:
func getMonday(myDate: Date) -> Date {
let cal = Calendar.current
var comps = cal.dateComponents([.weekOfYear, .yearForWeekOfYear], from: myDate)
comps.weekday = 2 // Monday
let mondayInWeek = cal.date(from: comps)!
return mondayInWeek
}
Note that printing a Date always uses the GMT time zone,
you'll need a date formatter to print the result according to your local time zone. Example:
let df = DateFormatter()
df.dateFormat = "yyyy-MM-dd HH:mm"
let now = Date()
print(df.string(from: now)) // 2016-10-02 20:16
let monday1 = getMonday(myDate: now)
print(df.string(from: monday1)) // 2016-09-26 00:00