I was wondering if I could somehow use the local timezone via the user's phone to convert the when the game starts for them (i.e. 9 if they are EST, 8 if they are CST, etc.)
I currently get the local time from the users phone:
let gmtTime = NSDate()
Then use that time to only display items in the present or future:
let query = PFQuery(className: "data")
query.orderByAscending("dateGame")
query.whereKey("dateGame", greaterThanOrEqualTo: gmtTime)
Using the dateGame (which is in UTC time) from my Parse backend:
Instead of having to hardcode one standard timezone time for every game start (9 EST):
Any ideas if this is possible?
NSDateFormatter can help you convert the start time to the user's local timezone.
var dateFormatter = NSDateFormatter()
dateFormatter.timeZone = NSTimeZone.localTimeZone()
dateFormatter.dateFormat = "h z"
let startTime = dateFormatter.stringFromDate(dateGame)
Related
In swift, the current time Date() is retrieved from the system time of iPhone. Using DateFormatter() seems to work the same way with a given string. For example, using the following method, we can get the same result as calling Date() right when the iPhone time reaches 2018/04/01 02:00:00
let MY_DATE_STRING = "2018/04/01 02:00:00"
var resultTime: Date {
let formatter = DateFormatter()
formatter.dateFormat = "yyyy/MM/dd HH:mm:ss"
formatter.timeZone = TimeZone.current
return formatter.date(from: MY_DATE_STRING)!
}
My question is, let's say, if 2018/04/01 2:00:00 is the end of daylight saving time, so the iPhone will have two 2am on that day -- one is with DST, while the other is not. These two times should have different UTC timestamp though. If currently the iPhone(or my self-defined MY_DATE_STRING) just enters the second 2am, which is a non-DST one, how could I set the TimeZone or other attributes so that the Date() or the given MY_DATE_STRING could generate the timestamp of second 2am instead of the first one?
So I would like that all my users would have the same date and time no matter their location. Even if they have changed date and time settings the date and time in the application would not change.
At the moment I have constructed a string which is based on every user's 'iPhone time'.
let todaysDate: String = {
let date = Date()
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd"
let result = formatter.string(from: date)
return result
}()
My wish is that every user would have EET (Eastern Europe Time).
Just set the time zone of your dateformatter to EET if you need the time/date to be independent of user location.
formatter.timeZone = TimeZone(abbreviation: "EET")
However, Date() returns the current device time, so if the user changes their date/time setting, you would get wrong results. To always get a correct data, you have to rely on a date fetched from a reliable server.
how can i return a NSDate in a predefined time zone from a string
let responseString = "2015-8-17 GMT+05:30"
var dFormatter = NSDateFormatter()
dFormatter.dateFormat = "yyyy-M-dd ZZZZ"
var serverTime = dFormatter.dateFromString(responseString)
println("NSDate : \(serverTime!)")
the above code returns the time as
2015-08-16 18:30:00 +0000
The date format has to be assigned to the dateFormat property of the date formatter instead.
let date = NSDate.date()
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
let str = dateFormatter.stringFromDate(date)
println(str)
This prints the date using the default time zone on the device. Only if you want the output according to a different time zone then you would add for example
Swift 3.*
dateFormatter.timeZone = NSTimeZone(name: "UTC")
Swift 4.*
dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
also refer link http://www.brianjcoleman.com/tutorial-nsdate-in-swift/
how can i return a NSDate in a predefined time zone?
You can't.
An instance of NSDate does not carry any information about timezone or calendar. It just simply identifies one point in universal time.
You can interpret this NSDate object in whatever calendar you want. Swift's string interpolation (the last line of your example code) uses an NSDateFormatter that uses UTC (that's the "+0000" in the output).
If you want the NSDate's value as a string in the current user's calendar you have to explicitly set up a date formatter for that.
Swift 4.0
dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
If you always have the same time zone for the input string, you can create two date formatters to output the local time zone (or a specified one):
let timeFormatterGet = DateFormatter()
timeFormatterGet.dateFormat = "h:mm a"
timeFormatterGet.timeZone = TimeZone(abbreviation: "PST")
let timeFormatterPrint = DateFormatter()
timeFormatterPrint.dateFormat = "h:mm a"
// timeFormatterPrint.timeZone = TimeZone(abbreviation: "EST") // if you want to specify timezone for output, otherwise leave this line blank and it will default to devices timezone
if let date = timeFormatterGet.date(from: "3:30 PM") {
print(timeFormatterPrint.string(from: date)). // "6:30 PM" if device in EST
} else {
print("There was an error decoding the string")
}
The number 1 means 1 regardless of language. Yet in English it's spelled as one, in Spanish it's una, in Arabic it wahid, etc.
Similarly 123982373 seconds pass 1970 is going to reflect differently in different timezones or calendar formats, but's all still 123982373 seconds passed 1970
The difference between 3 seconds and 7 seconds is 4 seconds. That doesn't require a calendar. Neither you need a calendar/timezone to know the difference in time between these two Epoch times 1585420200 and 1584729000
Dates are just a timeInterval from January 1, 1970 (midnight UTC/GMT). Dates also happen to have a string representation.
Repeating Nikolia's answer, Swift's default string interpolation (2015-08-16 18:30:00 +0000) uses a DateFormatter that uses UTC (that's the "+0000" in the output).
Calendars with the use of timezones give us a contextual representation that is just easier to understand than trying to calculate the difference between two gigantic numbers.
Meaning a single date (think of a single timeInterval since 1970) will have a different string interpretations per calendar. On top of that a calendar will itself vary based on time zones
I highly recommend that you go and play around with this Epoch converter site and see how selecting a different timezone will cause the string representations for the same moment/date/timeInterval to change
I also recommend to see this answer. Mainly this part:
Timezone is just an amendment to the timestamp string, it's not considered by the date formatter.
To consider the time zone you have to set the timeZone of the formatter
dateFormatter.timeZone = TimeZone(secondsFromGMT: -14400)
I currently have a integer variable for the hour of a current day, I calculated it like this:
let tz = NSTimeZone.defaultTimeZone()
let now = NSCalendar.currentCalendar().componentsInTimeZone(tz, fromDate: NSDate())
let currHour: Int = now.hour //6 for 6:35PM (current time)
How do I convert this to a string given the iPhone's current time settings. For example, my phone is set to 24-hour times while another iPhone is not. Using the Starbucks app as an example, looking at local stores, it will say either "Open until 22:00" on my phone or "Open until 10:00PM" on the other phone.
The defaultTimeZone is set to America/New_York in the app delegate.
NSDateFormatter does this automatically. Just set the timeStyle to .ShortStyle.
let formatter = NSDateFormatter()
formatter.dateStyle = .NoStyle
formatter.timeStyle = .ShortStyle
let timeString = formatter.stringFromDate(NSDate())
The value for timeString will be appropriate for the user's locale and their device settings.
I generate a NSDate object from string.
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
dateFormatter.timeZone = NSTimeZone(abbreviation: "GMT")
let stringToDate = dateFormatter.dateFromString(dateFromService) // 2015-07-20 12:00:43 +0000
I get this string value from webserver. I need to modify for personal device timezone. Want to add hours this stringToDate object but not work
var addHours : Int = 2 // 2 hours will be added
var newDate = stringToDate.dateByAddingTimeInterval(addHours)
Use NSCalendarComponents:
let calendar = NSCalendar.currentCalendar()
let newDate = calendar.dateByAddingUnit(
.CalendarUnitHour, // adding hours
value: 2, // adding two hours
toDate: oldDate,
options: .allZeros
)
Using NSCalendar will account for things like leap seconds, leap hours, etc.
But as Duncan C's answer points out, simply adding hours is definitely the wrong approach. Two time zones won't always be separated by the same amount of time. Again, this is something especially true when we take daylight savings into account. (For example, the United States doesn't start/end daylight savings on the same days as Europe, and Arizona doesn't even do daylight savings).
You're asking the wrong question. This is what's known as an "XY Problem".
You should be asking "How do I display a date string I get from a web server in the user's local time zone."
NSDate represents a date/time in an abstract form that does not contain a time zone. You convert it to a specific time zone for display. Do not try to add/subtract hours to an NSDate to offset for time zones. That is the wrong approach.
The correct answer is simple. Create a second date formatter and don't set it's timezone to GMT. It defaults to the user's local time zone.
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
dateFormatter.timeZone = NSTimeZone(abbreviation: "GMT")
let date = dateFormatter.dateFromString(dateFromService)
let outputDatedateFormatter = NSDateFormatter()
outputDatedateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
//leave the time zone at the default (user's time zone)
let displayString = outputDateFormatter.stringFromDate(date)
println("Date in local time zone = \(displayString)")
For Swift 3 you can use this function:
//get next date by adding hours func
getNewDateAfterAddingHours(hoursToAdd:NSInteger, oldDate:Date) -> Int64 {
let calendar = Calendar.current
let newDate = calendar.date(byAdding: .hour, value: hoursToAdd, to: oldDate)
return Int64((newDate?.timeIntervalSince1970)!)
}
If you are doing it more often, check out library called SwiftMoment (inspired by the same .js library), which allows you to do following (and much more!):
// Create date using moment library
let myDate = moment(myString)
// Add one hour
let dateWithAddedHour = myDate + 1.hours
Moment is a wrapper around NSDate instance, while Duration (which is what you get from Int.hours, Int.minutes etc.) wraps an NSTimeInterval value.
Implementing this should take you just a moment! (Pun intended).