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I want to get date of particular day for every week.
Suppose I have a date: 2017-04-13. It is an April, and 13 April is Thursday. I need to get every date in April which is Thursday.
How can I do this?
The output should be: 2017-04-06, 2017-04-13, 2017-04-20, 2017-04-27
Short solution:
// Get current calendar and current date
let calendar = Calendar.current
let now = Date()
// Get the current date components for year, month, weekday and weekday ordinal
var components = calendar.dateComponents([.year, .month, .weekdayOrdinal, .weekday], from: now)
// get the range (number of occurrences) of the particular weekday in the month
let range = calendar.range(of: .weekdayOrdinal, in: .month, for: now)!
// Loop thru the range, set the components to the appropriate weekday ordinal and get the date
for ordinal in range.lowerBound..
Be aware that print prints dates always in UTC.
Edit:
range(of: .weekdayOrdinal, in: .month does not work, it returns 1..<6 regardless of the date.
This is a working alternative. It checks if the date exceeds the month bounds
// Get current calendar and date for 2017/4/13
let calendar = Calendar.current
let april13Components = DateComponents(year:2017, month:4, day:13)
let april13Date = calendar.date(from: april13Components)!
// Get the current date components for year, month, weekday and weekday ordinal
var components = calendar.dateComponents([.year, .month, .weekdayOrdinal, .weekday], from: april13Date)
// Loop thru the range, set the components to the appropriate weekday ordinal and get the date
for ordinal in 1..<6 { // maximum 5 occurrences
components.weekdayOrdinal = ordinal
let date = calendar.date(from: components)!
if calendar.component(.month, from: date) != components.month! { break }
print(calendar.date(from: components)!)
}
Try this playground:
import UIKit
let dateString = "2017-04-13"
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
let referenceDate = dateFormatter.date(from: dateString)!
let calendar = Calendar.current
let firstDayComponents = calendar.dateComponents([.year, .month], from: referenceDate)
let monthFirst = calendar.date(from: firstDayComponents)!
let weekDay = calendar.component(.weekday, from: referenceDate)
var oneDay = DateComponents()
oneDay.day = 1
var checkDate = monthFirst
while calendar.component(.month, from: checkDate) == calendar.component(.month, from: referenceDate) {
if calendar.component(.weekday, from: checkDate) == weekDay {
let thisDay = dateFormatter.string(from: checkDate)
print(thisDay)
}
checkDate = calendar.date(byAdding: oneDay, to: checkDate)!
}
This code does the job. I added some logs to understand some logic behind it.
You can set dateInit as you wish, the rest of the code will find all the days that have the same weekday in the same year of the same month.
I printed two versions of date representations (NSDate objects and NSString objects), for the one having issue with timezones and "it's not the same day" cries.
It uses enumerateDatesStartingAfterDate:matchingComponents:options:usingBlock:
NSCalendar *calendar = [NSCalendar calendarWithIdentifier:NSCalendarIdentifierGregorian];
NSString *dateStr = #"2017-04-13";
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd"];
NSDate *dateInit = [dateFormatter dateFromString:dateStr];
NSLog(#"dateInit: %#", dateInit);
NSDateComponents *componentsToMatch = [calendar components:(NSCalendarUnitMonth|NSCalendarUnitWeekday) fromDate:dateInit];
NSDate *startOfMonth = [calendar dateFromComponents:[calendar components:(NSCalendarUnitYear|NSCalendarUnitMonth) fromDate:dateInit]];
NSLog(#"StartOfTheMonth: %#", startOfMonth);
NSArray *daysToFind = #[#"2017-04-06", #"2017-04-13", #"2017-04-20", #"2017-04-27"]; //According to author
NSLog(#"DaysToFind: %#", daysToFind);
NSMutableArray *allDaysInMonthMatchingWeekDay = [[NSMutableArray alloc] init];
[calendar enumerateDatesStartingAfterDate:startOfMonth
matchingComponents:componentsToMatch
options:NSCalendarMatchStrictly
usingBlock:^(NSDate * _Nullable date, BOOL exactMatch, BOOL * _Nonnull stop) {
NSLog(#"DateBlock: %#", date);
[allDaysInMonthMatchingWeekDay addObject:date];
}];
NSLog(#"allDaysInMonthMatchingWeekDay: %#",allDaysInMonthMatchingWeekDay);
for (NSDate *aDate in allDaysInMonthMatchingWeekDay)
{
NSLog(#"Found: %#", [dateFormatter stringFromDate:aDate]);
}
The logs:
$>dateInit: 2017-04-12 22:00:00 +0000
$>StartOfTheMonth: 2017-03-31 22:00:00 +0000
$>DaysToFind: (
"2017-04-06",
"2017-04-13",
"2017-04-20",
"2017-04-27"
)
$>DateBlock: 2017-04-05 22:00:00 +0000
$>DateBlock: 2017-04-12 22:00:00 +0000
$>DateBlock: 2017-04-19 22:00:00 +0000
$>DateBlock: 2017-04-26 22:00:00 +0000
$>allDaysInMonthMatchingWeekDay: (
"2017-04-05 22:00:00 +0000",
"2017-04-12 22:00:00 +0000",
"2017-04-19 22:00:00 +0000",
"2017-04-26 22:00:00 +0000"
)
$>Found: 2017-04-06
$>Found: 2017-04-13
$>Found: 2017-04-20
$>Found: 2017-04-27
Note: For the componentsToMatch, I tried to set the Year/Month/WeekDay flags unit, but the enumeration stopped at the first occurence, didn't search long why, I came up with only month and weekday flag to get it work. Maybe some little issue that I missed.
EDIT:
In Swift 3 (it works, but since I'm an Objective-C developer and not a Swift one, it may have issues, like wrapping/unwrapping etc)
let calendar = NSCalendar.init(calendarIdentifier: .gregorian)
let dateStr = "2017-04-13"
let dateFormatter = DateFormatter.init()
dateFormatter.dateFormat = "yyyy-MM-dd"
let dateInit = dateFormatter.date(from: dateStr)!
print("dateInit: \(dateInit)")
let componentsToMatch = calendar?.components([.month,.weekday], from: dateInit)
let startOfMonth = calendar?.date(from: (calendar?.components([.year,.month], from: dateInit))!)
print("StartOfTheMonth:\(startOfMonth)")
calendar?.enumerateDates(startingAfter: startOfMonth!, matching: componentsToMatch!, options: .matchStrictly, using: { (date, extactMatch, stop) in
print("DateBlock: \(date)")
})
I would write an extension for Calendar for any given time span and use an enum to name the weekdays
enum WeekDay: Int {
case sunday = 1
case monday
case tuesday
case wednesday
case thursday
case friday
case saturday
}
struct TimeSpan {
let startDate: Date
let endDate: Date
}
extension Calendar {
func allOccurrenceOf(day: WeekDay, in timeSpan:TimeSpan) -> [Date] {
let startDateWeekDay = Int(self.component(.weekday, from: timeSpan.startDate))
let desiredDay = day.rawValue
let offset = (desiredDay - startDateWeekDay + 7) % 7
let firstOccurrence = self.startOfDay(for:self.date(byAdding: DateComponents(day:offset), to: timeSpan.startDate)!)
guard firstOccurrence.timeIntervalSince1970 < timeSpan.endDate.timeIntervalSince1970 else {
return []
}
var filtered = [firstOccurrence]
while true {
let nextDate = self.date(byAdding: DateComponents(day: 7), to: filtered.last!)!
if nextDate < timeSpan.endDate {
filtered.append(nextDate)
break
}
}
return filtered
}
}
Beware that I hacked this could rather fast. I am sure that this can be expressed swiftier. In real production code I would also try to eliminate all ! from it.
usage:
let tuesdays = Calendar.autoupdatingCurrent.allOccurrenceOf(day: .tuesday, in: TimeSpan(startDate: Date(), endDate: Calendar.autoupdatingCurrent.date(byAdding: DateComponents(month:1), to: Date())!))
As Suggested in comment. see updated code. updated with week day
func getNumberOfDaysInMonth (month : Int , Year : Int, weekday: Int) -> [String]{
let dateComponents = NSDateComponents()
dateComponents.year = Year
dateComponents.month = month
let calendar = Calendar.current
let date = calendar.date(from: dateComponents as DateComponents)
let range = calendar.range(of: .day, in: .month, for: date!)
let numDays:Int = (range?.upperBound)!
let thuFormatter = DateFormatter()
var dateArray:[String] = [String]()
thuFormatter.dateFormat = "yyyy-MM-dd"
for day in 1...numDays {
dateComponents.day = day
let date2 = calendar.date(from: dateComponents as DateComponents)
print(calendar.component(.weekday, from: date2!))
if calendar.component(.weekday, from: date2!) == weekday
{
let dateThu = thuFormatter.string(from: date2!)
dateArray.append(dateThu)
}
}
return dateArray
}
and then call it like
let myThu:[String] = getNumberOfDaysInMonth(month: 4, Year: 2017,weekday: 3)
print(myThu)
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
I have 2 dates that I would like to compare. A date in the future, and the current date. When I compare them I want to retrieve their difference in terms of hours, minutes, and seconds. I believe the code I have to do this is correct, however, I get different values returned depending on the components I request.
I am using the following calendar for all examples:
let calendar = NSCalendar.currentCalendar()
A:
let dateComponents = calendar.components([NSCalendarUnit.Year, NSCalendarUnit.Month, NSCalendarUnit.Day, NSCalendarUnit.Hour, NSCalendarUnit.Second, NSCalendarUnit.Minute], fromDate: NSDate(), toDate: date, options: [])
B:
let dateComponents2 = calendar.components(.Hour, fromDate: NSDate(), toDate: date, options: [])
So, with the above example, dateComponents.hour does not equal dateComponents2.hour, and dateComponents2.hour returns the correct value.
Even more interesting is the following case:
A:
let dateComponents = calendar.components([NSCalendarUnit.Year, NSCalendarUnit.Month, NSCalendarUnit.Day, NSCalendarUnit.Hour, NSCalendarUnit.Second, NSCalendarUnit.Minute], fromDate: NSDate(), toDate: date, options: [])
B:
let dateComponents2 = calendar.components(.Minute, fromDate: NSDate(), toDate: date, options: [])
Now, dateComponents.minute does not equal dateComponents2.minute, but now dateComponents.minute returns the correct value.
Why could this be happening? Does the fact that I am requesting multiple components at the same time affect the return value?
EDIT
Here are some examples using the following dates. The return values are shown as hours, minutes, seconds:
2015-11-29 10:59:00 +0000
2015-11-28 07:57:20 +0000
Using dateComponents:
3, 1, 39
Using dateComponents2 (one for each component):
27, 1621, 97299
The hours value is correct from dateComponents2, and the minutes and seconds values are correct from dateComponents.
Let's imagine that the two NSDate objects are 61 seconds apart, if you get both minute and second at the same time, you get 1 minute and 1 second, but if you just ask for just seconds, you get 61 seconds:
let date1 = NSDate()
let date2 = date1.dateByAddingTimeInterval(61)
let calendar = NSCalendar.currentCalendar()
let components1 = calendar.components([.Minute, .Second], fromDate: date1, toDate: date2, options: [])
let components2 = calendar.components([.Second], fromDate: date1, toDate: date2, options: [])
print("\(components1.minute) minute and \(components1.second) second")
print("\(components2.second) seconds")
That yields:
1 minute and 1 second
61 seconds
Using your dates (and adding days and hours to the calculations):
let dateString1 = "2015-11-28 07:57:20 +0000"
let dateString2 = "2015-11-29 10:59:00 +0000"
let formatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss Z"
let date1 = formatter.dateFromString(dateString1)!
let date2 = formatter.dateFromString(dateString2)!
let calendar = NSCalendar.currentCalendar()
let components1 = calendar.components([.Day, .Hour, .Minute, .Second], fromDate: date1, toDate: date2, options: [])
let components2 = calendar.components([.Second], fromDate: date1, toDate: date2, options: [])
print("\(components1.day) day, \(components1.hour) hours, \(components1.minute) minute, and \(components1.second) seconds")
print("\(components2.second) seconds")
That yields:
1 day, 3 hours, 1 minute, and 40 seconds
97300 seconds
And if you multiply that out, you'll see that 1 day, 3 hours, 1 minute and 40 seconds is equal to 97300 seconds.
You can also consider using NSDateComponentsFormatter to create a nicely formatted (and localized) string representation of the time elapsed:
let componentsFormatter = NSDateComponentsFormatter()
componentsFormatter.allowedUnits = [.Day, .Hour, .Minute, .Second]
componentsFormatter.unitsStyle = .Full
print(componentsFormatter.stringFromDate(date1, toDate: date2))
// or just show the top two units (because if you're showing days/hours, you probably no longer care about minutes/seconds
componentsFormatter.maximumUnitCount = 2
print(componentsFormatter.stringFromDate(date1, toDate: date2))
// but if you want actual total number of seconds, then change `allowedUnits` to use only that
componentsFormatter.allowedUnits = [.Second]
print(componentsFormatter.stringFromDate(date1, toDate: date2))
That will display three optional strings:
1 day, 3 hours, 1 minute, 40 seconds
1 day, 3 hours
97,300 seconds
I have come across a rather strange "bug". When getting a date for a week of a year using this method:
let dates = NSMutableArray()
let cal = NSCalendar.currentCalendar()
cal.firstWeekday = 2
let formatter = NSDateFormatter()
formatter.dateFormat = "ww YYYY"
formatter.calendar = cal
let date = formatter.dateFromString(week as String)
println(date)
The string week is 52 2014, so the expected date would be Monday December 22th, but instead it returns Saturday December 20th, at 23:00. First of all, I thought I'd handled the first day of week by setting the firstWeekday-option of the calendar, but no luck. In addition, the date returned isn't even in week 52.
Just to double check I ran cal.components(NSCalendarUnit.WeekOfYearCalendarUnit, fromDate: date!).weekOfYear to double check I'm not an idiot, and no sir, the week for the date produced is 51, the week before the desired week.
Any idea how I can reach the expected result?
Any idea how I can reach the expected result?
What actually is your desired result? Do you want to know the first day of the week or the first day in the last day? Than you could tray this:
let now = NSDate()
var startDate: NSDate? = nil
var duration: NSTimeInterval = 0
let cal = NSCalendar.currentCalendar()
cal.firstWeekday = 2
cal.rangeOfUnit(.WeekCalendarUnit, startDate: &startDate, interval: &duration, forDate: now);
let endDate = startDate?.dateByAddingTimeInterval(duration)
print(startDate)
print(endDate)
it prints
"Optional(2014-12-21 23:00:00 +0000)"
"Optional(2014-12-28 23:00:00 +0000)"
the endDate is the first second that is not in the week anymore.
Note that the offset of 1 hour results from the fact that it is printed in UTC time, that is actually GMT winter time. Indeed these dates are 2014-12-22 00:00:00 and 2014-12-29 00:00:00 in my time zone (GMT+1)
or simply
let components = NSDateComponents()
components.weekOfYear = 52
components.weekday = 2
components.year = 2014
let cal = NSCalendar.currentCalendar()
let day = cal.dateFromComponents(components)
This code adapted to respect user's calendar:
let cal = NSCalendar.currentCalendar()
let components = NSDateComponents()
components.weekOfYear = 52
components.weekday = cal.firstWeekday
components.year = 2014
Changing the firstWeekday from 1 to 2 won't change the date, it will change just the First weekday from Sunday to Monday.
You can do it like this:
func dateFromWeekOfYear(year:Int, weekOfYear:Int, weekday:Int) -> NSDate {
return NSCalendar.currentCalendar().dateWithEra(1, yearForWeekOfYear: year, weekOfYear: weekOfYear, weekday: weekday, hour: 0, minute: 0, second: 0, nanosecond: 0)!
}
let date1 = dateFromWeekOfYear(2014, 52, 1) // Dec 21, 2014, 12:00 AM
let date2 = dateFromWeekOfYear(2014, 52, 2) // Dec 22, 2014, 12:00 AM
let date3 = dateFromWeekOfYear(2014, 52, 3) // Dec 23, 2014, 12:00 AM
If dealing with a string and you want to set he Stand Alone local day of week you can do it like this:
let myDate = "2 52 2014"
let cal = NSCalendar.currentCalendar()
let formatter = NSDateFormatter()
formatter.dateFormat = "c ww Y"
formatter.calendar = cal
if let date1 = formatter.dateFromString(myDate) {
date1 // "Dec 22, 2014, 12:00 AM"
}
If you need further reference you can use this: