My problem is that I save a date into a string and as a date in CoreData. Later, I need to pull the date out of the string, compare the two, and find that they're the same date. Right now, that equality check fails. The two dates are 7 hours apart but with the minutes correct. I think it's a timezone issue but I can't figure out how to solve it.
The Origin of the Dates
I have a date from a date picker that I save to CoreData like this:
task.setValue(dueDatePicker.date, forKey: "dueDate")
After that I format the date and insert that date into a message:
let dateFormatter = DateFormatter()
let dateFormat = DateFormatter.Style.medium
let timeFormat = DateFormatter.Style.short
dateFormatter.dateStyle = dateFormat
dateFormatter.timeStyle = timeFormat
let formattedDate = dateFormatter.string(from: date)
let message = ("Upcoming task on \(formattedDate)")
That message becomes part of a notification. Hours or days later (when the notification fires and the user selects an action) I get the CoreData date:
fetchRequest.predicate = NSPredicate(format: "dueDate = %#", dateOfTask)
Then I decompose the notification message and get the date:
let start = notifString.range(of: "on ")
let rawDate = notifString[(start.upperBound)!..<(notifString.endIndex)]
let dateFormatter = DateFormatter()
dateFormatter.timeZone =
dateFormatter.dateFormat = "MMM-d-yyyy, H:mm a"
let dateFromString = dateFormatter.date(from: rawDate)
Lastly, I compare them. Currently the times are clearly the same day and minute but the timezones differ by about 7 hours. However, I don't want to just force a timezone that matches (Maybe force UTC for example) because that may not work for a user in another location.
How do I retrieve both dates without getting this apparent timezone issue?
Blatantly obvious, use userInfo as #Paulw11 suggested:
newLocalNotif.fireDate = dueDateWarningTime
newLocalNotif.alertBody = message
newLocalNotif.timeZone = TimeZone.autoupdatingCurrent
newLocalNotif.soundName = UILocalNotificationDefaultSoundName
newLocalNotif.category = "DueDates"
newLocalNotif.userInfo = ["name": name, "desc": desc, "dueDate" : date]
Related
What do we got: Date+time (format yyyy-mm-dd hh:mm a)
What are we looking for: Time difference in minutes
What operation: NewDate - OldDate
So, I wonder how I could accomplish above goal? I would like to format the date and time to US, regardless from which locale the user has. How can I do that?
Then I will save the 'oldTime' into UserDefaults, and use it for later calculation. The goal is to put the user on delay for 5 minutes and the calculations will be performed to determine if user should be on delay or not.
Just make a function that takes two dates and compares them like this.
import UIKit
func minutesBetweenDates(_ oldDate: Date, _ newDate: Date) -> CGFloat {
//get both times sinces refrenced date and divide by 60 to get minutes
let newDateMinutes = newDate.timeIntervalSinceReferenceDate/60
let oldDateMinutes = oldDate.timeIntervalSinceReferenceDate/60
//then return the difference
return CGFloat(newDateMinutes - oldDateMinutes)
}
//Usage:
let myDateFormatter = DateFormatter()
myDateFormatter.dateFormat = "yyyy-MM-dd HH:mm"
//You'll need both dates to compare, you can get them by just storing a Date object when you first start the timer.
//Then when you need to check it, compare it to Date()
let oldDate: Date = myDateFormatter.date(from: String("2019-06-22 11:25"))
func validateRefresh() {
//do the comparison between the old date and the now date like this.
if minutesBetweenDates(oldDate, Date()) > 5 {
//Do whatever
}
}
You can, of course, change the .dateFormat value on the date formatter to be whatever format you'd like. A great website for finding the right format is: https://nsdateformatter.com/.
You say:
I would like to format the date and time to US, regardless from which locale the user has. How can I do that?
Specify a Locale of en_US_POSIX:
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd hh:mm a"
formatter.locale = Locale(identifier: "en_US_POSIX")
The locale is not the only question.
There’s also a timezone question. For example, you're driving out of Chicago and go from Central to Eastern timezones; do you really want to consider that one hour has passed?
Do you really want to discard seconds? If you do that, the 59 seconds between going from 8:00:00pm to 8:00:59pm will be considered “zero minutes” but the one second between 8:00:59pm and 8:01:00pm will be considered “one minute”.
Frankly, if I wanted to save a locale and timezone invariant date string, I’d suggest using ISO8601DateFormatter.
Then I will save the 'oldTime' into UserDefaults, and use it for later calculation.
If that’s why you’re using this DateFormatter, I’d suggest saving the Date object directly.
UserDefaults.standard.set(oldTime, forKey: "oldTime")
And to retrieve it:
if let oldTime = UserDefaults.standard.object(forKey: "oldTime") as? Date {
...
}
In terms of calculating the number of minutes between two Date objects
let minutes = Calendar.current
.dateComponents([.minute], from: date1, to: date2)
.minute
If you want the number of seconds, you can also use timeIntervalSince:
let seconds = date2.timeIntervalSince(date1)
And if you wanted to show the amount of elapsed time as a nice localized string:
let intervalFormatter = DateComponentsFormatter()
intervalFormatter.allowedUnits = [.minute, .second]
intervalFormatter.unitsStyle = .full
let string = intervalFormatter.string(from: date1, to: date2)
I'm not convinced that your question is the best way to go about accomplishing your aim, but the code below will work.
let dateFormatterNow = DateFormatter()
dateFormatterNow.dateFormat = "yyyy-MM-dd hh:mm a"
dateFormatterNow.timeZone = TimeZone(abbreviation: "EST")
let oldDateString = "2019-06-23 12:44 p"
let oldDate = dateFormatterNow.date(from: oldDateString)
let newDateString = "2019-06-23 12:54 p"
let newDate = dateFormatterNow.date(from: newDateString)
if let oldDate = oldDate, let newDate = newDate {
let diffInMins = Calendar.current.dateComponents([.minute], from: oldDate, to: newDate).minute
print(diffInMins)
}
I have the following string:
let dateString = "2018-04-18T04:54:00-04:00"
I initialize a Date via the ISO8601DateForamtter by doing the following:
let formatter = ISO8601DateFormatter()
let date = formatter.date(from: dateString)
If I print the date, I get the following:
Apr 18, 2018 at 1:54am
The formatter is automatically converting the time into my local time. How can I prevent accounting for my time zone? For example, I want the Date object to show the following instead:
Apr 18, 2018 at 4:54am
With ISO8601, 2018-04-18T04:54:00-04:00 means 2018-04-18 04:54:00 in GMT -4h. To print the time as it is in the original string, you need to create a date formatter with the specific time zone which is -4.
let dateFormatter = DateFormatter()
dateFormatter.timeZone = TimeZone(secondsFromGMT: -4 * 60 * 60)
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
print(dateFormatter.string(from: date))
You will get
2018-04-17 04:54:00
FYI, I'm adding a link for ISO8601
You need to parse the timezone from your date string and use it to set the timezone from your date formatter:
func secondsFromGMT(from string: String) -> Int {
guard !string.hasSuffix("Z") else { return 0 }
let timeZone = string.suffix(6)
let comps = timeZone.components(separatedBy: ":")
guard let hours = comps.first,
let minutes = comps.last,
let hr = Int(hours),
let min = Int(minutes) else { return 0 }
return hr * 3600 + min * 60
}
let dateString = "2018-04-18T04:54:00-04:00"
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssxxxxx"
formatter.locale = Locale(identifier: "en_US_POSIX")
if let dateFromString = formatter.date(from: dateString) {
formatter.timeZone = TimeZone(secondsFromGMT: secondsFromGMT(from: dateString))
formatter.dateFormat = "MMM dd, yyyy 'at' h:mma"
formatter.amSymbol = "am"
formatter.pmSymbol = "pm"
print(formatter.string(from: dateFromString)) // Apr 18, 2018 at 4:54am
}
Instead of logging the Date directly, have a look at the string(from:timeZone:formatOptions:) method on ISO8601DateFormatter. With this, you should be able to get a date string for any time zone you desire.
You should set your formatter to the appropriate timezone such as (UTC example below):
formatter.timeZone = TimeZone(identifier: "UTC")
or alternatively specify against GMT:
formatter.timeZone = TimeZone(secondsFromGMT: 0)
The date that you are receiving from your current formatter is technically correct. Setting the date backwards as described in the currently accepted answer is not advised because you are effectively hard-coding an intended time zone. As soon as your device enters another time zone (or if a user downloads your app outside of the current time zone), your information will be incorrect.
If you are trying to display this time in the UTC time zone, you need to use another formatter to correctly format the output in the target time zone.
let utcFormatter = DateFormatter()
utcFormatter.timeZone = TimeZone(secondsFromGMT: 0)
// Perform any other transformations you'd like
let output = utcFormatter.string(from: date)
But why is your original date correct?
The Date API is incredibly robust and doing a lot of things under-the-hood, but is effectively implemented using a simple Double. The automaic time-zone information that it's displaying to you is an abstraction to make it easier to reason about. A date technically has no knowledge of what time zone it's in – but converting it to a string implicitly applies an inferred date formatter on the date and returns information it thinks will be most useful to you.
If you're doing manipulations on a date, you're likely using the Calendar API. You typically get a new instance from using Calendar.current, which will create a new calendar with your current time zone information. You can change the represented time zone of the calendar like this:
var calendar = Calendar.current
calendar.timeZone = TimeZone(secondsFromGMT: 0)
This will give you relative dates that will work in any time zone without modifying the base Date object that you're working with.
when i'm going set event from app to device calendar. i got wrong time.
i have three date picker one for date and other two for start time and end time for event. i set start date as end date in EKEvent because i have to set event on that day only.
get date from date-picker and store it as startdate and end date as nsdate type. below is my date-picker method
func pickerDate()
{
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "YYYY-MM-dd"
routineStartDate = dateFormatter.string(from: self.startDatePicker.date)
// it is for database entry in string and i get right string
print(routineStartDate)
startDate = self.startDatePicker.date as NSDate
print(startDate)
endDate = startDate
}
below method is for start time where i get time and convert to Time Interval and set it to start date.
func starttime() {
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "HH:mm"
let then: Date? = self.startTimePicker.date
let difference: TimeInterval? = then?.timeIntervalSinceNow
startDate.addingTimeInterval(difference!)
routineStartTime = dateFormatter.string(from: self.startTimePicker.date)
// it is for database entry in string and i get right string
print(routineStartTime)
}
below method is for end time where i get time from picker and convert to Time Interval and set Time Interval to enddate
func endtime() {
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "HH:mm"
routineEndTime = dateFormatter.string(from: self.endTimePicker.date)
print(routineEndTime)
// it is for database entry in string and i get right string
let then: Date? = self.endTimePicker.date
let difference: TimeInterval? = then?.timeIntervalSinceNow
endDate.addingTimeInterval(difference!)
}
below image showing which date i set in picker
below is My EKEvent method where i create event.
existevent.title = tempDescription
existevent.startDate = startDate as Date
existevent.endDate = endDate as Date
existevent.isAllDay = false
existevent.notes = "This is a note"
existevent.calendar = cal
when i check event in calendar i got Problem, i get wrong time in event.i set start time 12:50 pm end time 1:50 pm on date 27 june 2017 in caledar app. date is set perfectly but why time is not set perfectly ? below image for calendar app.
i have doubt in conversion of time interval and set to date. but what i missing dont know.
please suggest me solution and ideas to solve.
Thank you
you need to convert the time to the desired time zone. Because now the date is set correctly in your timezone, but is displayed in +0000 Screenshot. Use calendar for date representation this
And change your code like this in both methods:
startDate.addingTimeInterval(difference!)
to
self.startDate = startDate.addingTimeInterval(difference!)
and
endDate.addingTimeInterval(difference!)
to
self.endDate = endDate.addingTimeInterval(difference!)
in your case Xcode Warning "Result of call to 'addingTimeInterval' is unused"
Try to convert date, before set it to you "existevent", or when you show it
func convertDate(date:Date) -> Date {
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "HH:mm" // or other format
var comp = DateComponents()
let calendar = Calendar.current
comp.hour = Calendar.current.component(.hour, from: date)
comp.minute = Calendar.current.component(.minute, from: date)
comp.timeZone = TimeZone(abbreviation: "GMT")!
return calendar.date(from: comp)!
}
Assume I'm given an input string like "7:00". I know that the time is EST but I want to convert it to localized time (so for people in PST it says 4:00). I tried the following code, but I keep getting a 24-hour time from it and the complete date (e.g: Optional(2000-01-01 16:00:00 +0000)). I want just the hour:min time...what am I doing wrong?
var dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "HH:mm"
dateFormatter.timeZone = NSTimeZone.localTimeZone()
gameClock = "\(dateFormatter.dateFromString("7:30"))"
println(gameClock)
You need to specify the time zone for your date formatter that you use to process the server date. By default, the time zone of the date formatter is the default time zone of the device.
So, for your above code, you should do this:
let dateStringFromServer = "07:00"
let serverDateFormatter = NSDateFormatter()
serverDateFormatter.dateFormat = "HH:mm"
serverDateFormatter.timeZone = NSTimeZone(name: "EST")
let dateFromServer = serverDateFormatter.dateFromString(dateStringFromServer)
let localDateFormatter = NSDateFormatter()
serverDateFormatter.dateFormat = "HH:mm"
let localizedStringForThatDate = localDateFormatter.stringFromDate(dateFromServer!)
The dateFormatter.dateFromString("7:30") gives you an NSDate not an NSString. You have make use of another NSDateFormatter object to get the date in desired string format.
let dateFormatterForDisplay = NSDateFormatter();
dateFormatterForDisplay.dateFormat = "HH:mm"
dateFormatterForDisplay.locale = NSLocale(localeIdentifier: "en_US_POSIX")
(you need the last line in the above if you want to force 12 hour mode, the default is NSLocale.currentLocale() and can be 12 hr or 24 hr mode for different locales)
Then
let displayString = dateFormatterForDisplay.stringFromDate(gameClock)
I'm making an app where i get time from Parse as String e.g. "13:24" i need to prepare it to save in CoreData as Date, but replacing the time with this String to use it later in fireDate notification. What's the best approach to do this ? I should get the currentDate(), change it into string and somehow replace it with my timeString from Parse ?
You can use this snippet to get todays date + custom time:
let time = "12:34"
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy/MM/dd HH:mm"
var todayDateString = dateFormatter.stringFromDate(NSDate())
todayDateString.replaceRange(Range<String.Index>(start: todayDateString.endIndex.advancedBy(-5), end: todayDateString.endIndex), with: time)
let newDate = dateFormatter.dateFromString(todayDateString)