Try the following in playgrounds. Before iOS 12, it worked for all inputs (starting with 1):
input would equal output
let input = 1
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
var dateComponents = DateComponents()
dateComponents.day = input
dateComponents.hour = 0
dateComponents.minute = 0
dateComponents.second = 0
let date = Calendar.current.date(from: dateComponents)
let dateString = dateFormatter.string(from: date!)
let date2 = dateFormatter.date(from: dateString)
let output = Calendar.current.ordinality(of: .day, in: .era, for: date2!)
assert(output==input)
But, now in iOS 12, output and input will only be equal starting with an input of 577738... which is date: Oct 17, 1582, which is two days after the Gregorian calendar went into effect (source: https://en.wikipedia.org/wiki/Gregorian_calendar)
So, what's going on here? And why did this change in iOS 12?
Related
I’m trying to convert my AM PM time pickers to 24h format to print the start and end time to calculate the price but i got an unknown error. attached is photo of my UI to simplify the idea and my code.
Note: the end time is automatically shows after i choose the start time
#objc func donePressed(){
// formatter
let formatter = DateFormatter()
formatter.dateStyle = .none
formatter.timeStyle = .short
startTimeTxt.text = formatter.string(from: StartTimePicker.date)
self.view.endEditing(true)
endTimeTxt.text = formatter.string(from: EndTimePicker.date)
self.view.endEditing(true)
let starttimecal = StartTimeTxt.text!
let endtimecal = EndTimeTxt.text!
let StartTo24 = starttimecal
let EndTo24 = endtimecal
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "h:mm a"
let sTime = dateFormatter.date(from: startTo24)
dateFormatter.dateFormat = "HH:mm"
let sTime24 = dateFormatter.string(from: sTime!)
print("24 hour formatted Date:", sTime24)
let eTime = dateFormatter.date(from: endTo24)
dateFormatter.dateFormat = "HH:mm"
let eTime24 = dateFormatter.string(from: eTime!) // here the fatal error comes after i choose the start time from simulator
print("24 hour formatted Date:", eTime24)
}
To get the 12h time format to display in the text fields you can use the formatter you already have but I also like to set the locale
let dateFormatter12h = DateFormatter()
dateFormatter12h.locale = Locale(identifier: "en_US_POSIX")
dateFormatter12h.dateFormat = "h:mm a"
To calculate the time difference there is a function for that in the Calendar class, here we calculate the number of hours and minutes between two dates (this is an assumption since I don't know exactly what calculation you want to do)
let hourAndMinutes = Calendar.current.dateComponents([.hour, .minute], from: startDate, to: endDate)
Below is a more complete example
//Sample data
let startDate = Date()
let endDate = startDate.addingTimeInterval(3.25*60*60) //add 3h and 15 minutes
// Format and print in 12h format
let dateFormatter12h = DateFormatter()
dateFormatter12h.locale = Locale(identifier: "en_US_POSIX")
dateFormatter12h.dateFormat = "h:mm a"
let start = dateFormatter12h.string(from: startDate)
let end = dateFormatter12h.string(from: endDate)
print(start, end)
// Calculate time difference in hours and minutes
let hourAndMinutes = Calendar.current.dateComponents([.hour, .minute], from: startDate, to: endDate)
print(hourAndMinutes)
// Calculate price, the formula is just an example
let price = hourAndMinutes.hour! * 15 + hourAndMinutes.minute! * 15 / 60
print(price)
Output
6:46 PM 10:01 PM
hour: 3 minute: 15 isLeapMonth: false
48
I am getting year,month and day from a given date in this way.
let today=Date()
var calendar = Calendar.current
calendar.timeZone = .current
let components = calendar.dateComponents([.year, .month, .day], from: today)
let day=components.day
But I'm getting one day ahead from my current day. How can I solve this?
let date = Date().description(with: Locale.current)
print("date ---> \(date)")
Result: date ---> Tuesday, June 20, 2017 at 4:35:15 PM India Standard Time
I'm getting perfect system/local time.
You code is working,
let today=Date()
var calendar = Calendar.current
calendar.timeZone = .current
let components = calendar.dateComponents([.year, .month, .day, .hour, .minute], from: today)
let day = components.day
let hour = components.hour
let minute = components.minute
print("day = \(day)\nhour = \(hour)\nminute = \(minute)")
Result: day = Optional(20) hour = Optional(16) minute = Optional(35)
Get Local Date and Time
Swift 5:
let today = Date()
let timeZone = Double(TimeZone.current.secondsFromGMT(for: today))
let localDate = Calendar.current.date(byAdding: .second, value: Int(timeZone), to: today) ?? Date()
As per the documentation:
If you want “date information in a given time zone” in order to
display it, you should use DateFormatter to format the date.
eg:
// If date is "Dec 7, 2018 at 6:34 AM" UTC
let today=Date() // is always UTC
var calendar = Calendar.current
calendar.timeZone = .current
let components = calendar.dateComponents([.year, .month, .day], from: today)
let day = components.day // Is 7
// To print with local version
let myFormatter = DateFormatter()
myFormatter.timeZone = TimeZone(secondsFromGMT: 3600*10)
myFormatter.dateFormat = "dd"
print(myFormatter.string(from: today)) // prints "07\n"
myFormatter.timeZone = TimeZone(secondsFromGMT: -3600*11)
print(myFormatter.string(from: today)) // prints "06\n"
When I run this code:
let calendar = Calendar.current
var dateComponents = DateComponents()
dateComponents.weekday = calendar.firstWeekday
dateComponents.weekOfYear = 2
dateComponents.year = 2017
let startOfWeek = calendar.date(from: dateComponents)
let endOfWeek = calendar.date(byAdding: .day, value: 6, to: startOfWeek!)
let formatter = DateFormatter()
formatter.dateStyle = .short
print(formatter.string(from: startOfWeek!))
print(formatter.string(from: endOfWeek!))
It prints this:
1/8/17
1/14/17
When I change the code to this:
dateComponents.weekOfYear = 1
dateComponents.year = 2017
It prints this:
12/31/17
1/6/18
Why is it 12/31/17?
When I use .full style to print the dates, I get Sunday, December 31, 2017 for the first date, but it's obviously wrong because December 31 is a Thursday.
If you want to get the correct date, use yearForWeekOfYear instead of year. Docs:
You can use the yearForWeekOfYear property with the weekOfYear and weekday properties to get the date corresponding to a particular weekday of a given week of a year. For example, the 6th day of the 53rd week of the year 2005 (ISO 2005-W53-6) corresponds to Sat 1 January 2005 on the Gregorian calendar.
Alternative, you can be a little naughty and not listen to the docs and use weekOfYear = 54:
let calendar = Calendar.current
var dateComponents = DateComponents()
dateComponents.weekday = calendar.firstWeekday
dateComponents.weekOfYear = 54
dateComponents.year = 2017
let startOfWeek = calendar.date(from: dateComponents)
let endOfWeek = calendar.date(byAdding: .day, value: 6, to: startOfWeek!)
let formatter = DateFormatter()
formatter.dateStyle = .short
print(formatter.string(from: startOfWeek!))
print(formatter.string(from: endOfWeek!))
This prints:
1/1/17
1/7/17
which is coincidentally, the correct dates.
I can get the 24 hour style time, but how do I get the 12 hour format with the am and pm?
let date = NSDate()
let calendar = NSCalendar.currentCalendar()
let components = calendar.components([.Hour, .Minute, .Second], fromDate: date)
let hour = components.hour
let minutes = components.minute
As you say, you should use NSDateFormatter for your desired format. Hope this will help you.
let date = NSDate()
let formatter = NSDateFormatter()
formatter.dateFormat = "hh:mm a"
let time = formatter.stringFromDate(date)
For more information about date formatter see NSDateFormatter
Swift 3.1 Answer
let date = Date() //Jun 1, 2017, 10:22 AM"
let formatter = DateFormatter() //<NSDateFormatter: 0x608000244380>
formatter.dateFormat = "hh:mm a" //<NSDateFormatter: 0x608000244380>
let time = formatter.string(from: date) //"10:22 AM"
Time format must be in 'hh' not HH
formatter.dateFormat = "hh:mm a"
let str=dict["startDateTime"] as! String //if the date is in the array
let str="16:00" //if you want to use static date
let index=str.index(str.startIndex, offsetBy: 11)
let end_index=str.index(str.endIndex, offsetBy:-3)
let dateAsString = str[index ..< end_index]
let dateFormatter=DateFormatter()
dateFormatter.dateFormat="HH:mm"
let date = dateFormatter.date(from: String(dateAsString))
dateFormatter.dateFormat = "h:mm a"
let Date12 = dateFormatter.string(from: date!)
print(Date12)
We can get day of year for date using below line.
let day = cal.ordinalityOfUnit(.Day, inUnit: .Year, forDate: date)
But how can we get the date from day of year?
If you know the year you can get DateComponents date property as follow:
extension Calendar {
static let iso8601 = Calendar(identifier: .iso8601)
}
let now = Date()
let day = Calendar.iso8601.ordinality(of: .day, in: .year, for: now)! // 121
let year = Calendar.iso8601.component(.year, from: now) // 2017
let date = DateComponents(calendar: .iso8601, year: year, day: day).date // "May 1, 2017, 12:00 AM"
or using DateFormatter
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy D"
if let date = dateFormatter.date(from: "\(year) \(day)") {
dateFormatter.dateStyle = .medium
dateFormatter.timeStyle = .short
dateFormatter.string(from: date) // "May 1, 2017, 12:00 AM"
}
You cannot go the other way. Going from a date to a day of the year discards all other information, you are left with only the day of the year (you no longer know what year). To go back to a full date you would have to make assumptions about the year the day was in.
The answer that #LeoDabus gave is more succinct than this, so it is perhaps the better choice. Having said that, this is the code that I would have used:
let dateComponents = NSDateComponents();
dateComponents.year = 2015
dateComponents.day = day
let calendar = NSCalendar.currentCalendar()
let date = calendar.dateFromComponents(dateComponents)
Updated for Swift 4:
let dateComponents = NSDateComponents();
dateComponents.year = 2018
dateComponents.day = someDay
let calendar = NSCalendar.current
let date = calendar.date(from: dateComponents as DateComponents)