iOS Swift - Get the Current Local Time and Date Timestamp

Question

I m trying to make an attendance app and I am really confused about date and time in iOS and Firebase   I use date as Key  this is the structure of my Firebase database   --Employees   --Unique ID      --Details           Name  John      --Attendance           --dateToday               Timein  8 00 AM               Timeout  5 00 PM               BreakStart  12 00 PM               BreakFinish  1 00 PM   This is my code to get the date timestamp I used as Key   override func viewDidLoad          super viewDidLoad         let now   NSDate        let nowTimeStamp   self getCurrentTimeStampWOMiliseconds dateToConvert  now           I save this dateToday as Key in Firebase      dateToday   nowTimeStamp     func getCurrentTimeStampWOMiliseconds dateToConvert  NSDate  - gt  String       let objDateformat  DateFormatter   DateFormatter       objDateformat dateFormat    yyyy-MM-dd      let strTime  String   objDateformat string from  dateToConvert as Date      let objUTCDate  NSDate   objDateformat date from  strTime   as NSDate     let milliseconds  Int64   Int64 objUTCDate timeIntervalSince1970      let strTimeStamp  String      milliseconds       return strTimeStamp     But when I convert it back to date I get 2017-09-22 16 00 00  0000  which is wrong because it is 23rd of September in my location   What is the right code to use so that I can get the correct date timestamp and time timestamp

User · Answer

First I would recommend you to store your timestamp as a NSNumber in your Firebase Database, instead of storing it as a String.

Another thing worth mentioning here, is that if you want to manipulate dates with Swift, you'd better use Date instead of NSDate, except if you're interacting with some Obj-C code in your app.

You can of course use both, but the Documentation states:

Date bridges to the NSDate class. You can use these interchangeably in code that interacts with Objective-C APIs.

Now to answer your question, I think the problem here is because of the timezone.

For example if you print(Date()), as for now, you would get:

2017-09-23 06:59:34 +0000

This is the Greenwich Mean Time (GMT).

So depending on where you are located (or where your users are located) you need to adjust the timezone before (or after, when you try to access the data for example) storing your Date:

    let now = Date()

    let formatter = DateFormatter()

    formatter.timeZone = TimeZone.current

    formatter.dateFormat = "yyyy-MM-dd HH:mm"

    let dateString = formatter.string(from: now)

Then you have your properly formatted String, reflecting the current time at your location, and you're free to do whatever you want with it :) (convert it to a Date / NSNumber, or store it directly as a String in the database..)

User · Answer

When we convert a UTC timestamp  2017-11-06 20 15 33 -08 00  into a Date object  the time zone is zeroed out to GMT  For calculating time intervals  this isn t an issue  but it can be for rendering times in the UI   I favor the RFC3339 format  2017-11-06T20 15 33-08 00  for its universality  The date format in Swift is yyyy-MM-dd T HH mm ssXXXXX but RFC3339 allows us to take advantage of the ISO8601DateFormatter   func getDateFromUTC RFC3339  String  - gt  Date        let formatter   ISO8601DateFormatter       return formatter date from  RFC3339      RFC3339 also makes time-zone extraction simple   func getTimeZoneFromUTC RFC3339  String  - gt  TimeZone         switch RFC3339 suffix 6         case   05 30           return TimeZone identifier   Asia Kolkata        case   05 45           return TimeZone identifier   Asia Kathmandu        default          return nil             There are 37 or so other time zones we d have to account for and it s up to you to determine which ones  because there is no definitive list  Some standards count fewer time zones  some more  Most time zones break on the hour  some on the half hour  some on 0 45  some on 0 15   We can combine the two methods above into something like this   func getFormattedDateFromUTC RFC3339  String  - gt  String         guard let date   getDateFromUTC RFC3339  RFC3339           let timeZone   getTimeZoneFromUTC RFC3339  RFC3339  else               return nil            let formatter   DateFormatter       formatter dateFormat    h mma EEE  MMM d yyyy      formatter amSymbol    AM      formatter pmSymbol    PM      formatter timeZone   timeZone    preserve local time zone     return formatter string from  date       And so the string  2018-11-06T17 00 00 05 45   which represents 5 00PM somewhere in Kathmandu  will print 5 00PM Tue  Nov 6 2018  displaying the local time  regardless of where the machine is   As an aside  I recommend storing dates as strings remotely  including Firestore which has a native date object  because  I think  remote data should agnostic to create as little friction between servers and clients as possible

User · Answer

If you just want the unix timestamp  create an extension   extension Date       func currentTimeMillis   - gt  Int64           return Int64 self timeIntervalSince1970   1000            Then you can use it just like in other programming languages   let timestamp   Date   currentTimeMillis

User · Answer

in Swift 5  extension Date       static var currentTimeStamp  Int64          return Int64 Date   timeIntervalSince1970   1000            call like this   let timeStamp   Date currentTimeStamp print timeStamp    Thanks  lenooh

User · Answer

you can even create a function to return different time stamps depending on your necessity   func dataatual   tipo Int  - gt  String           let date   Date           let formatter   DateFormatter           if tipo    1              formatter dateFormat    dd MM yyyy            else if tipo    2              formatter dateFormat    yyyy-MM-dd HH mm            else               formatter dateFormat    dd-MM-yyyy                     return formatter string from  date

User · Answer

The simple way to create Current TimeStamp  like below   func generateCurrentTimeStamp    - gt  String       let formatter   DateFormatter       formatter dateFormat    yyyy MM dd hh mm ss      return  formatter string from  Date    as NSString  as String

User · Answer

If you code for iOS 13 0 or later and want a timestamp  then you can use   let currentDate   NSDate now

User · Answer

For saving Current time to firebase database I use Unic Epoch Conversation   let timestamp   NSDate   timeIntervalSince1970   and For Decoding Unix Epoch time to Date     let myTimeInterval   TimeInterval timestamp  let time   NSDate timeIntervalSince1970  TimeInterval myTimeInterval

[ios] iOS Swift - Get the Current Local Time and Date Timestamp

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