DateFormatter() A Deep Vision

All iOS developers struggles with date formatter even though they go through a lot. Some times it behaves like an adorable kid can’t stay under control. So all we need is a deep vision in DateFormatter.

ALL WE NEED IS DATEFORMATTER

If we want process a Date, All we need is Apple’s DateFormatter class that has every thing we need. Here we will see how Date and Date Stringshad been processed in desired way.

Here are someways to process date:

1. Converting a Date Strings to a Date using one of the date formats of dateFormatter instance.
2. Converting a Date to a Date Stringsusing one of the date formats of dateFormatter instance.
3. Converting a Date instance to a Date Strings using a user defined format.
4. Converting Date Strings a instance to a Date using a user defined format.
5. Get Date from built-in Date Styles .

Formatter Language

1. yyyy — Defines year (eg: 2021)
2. MM — Defines Month in number(eg: 04)
3. MMM — Defines Month in word short(eg: Oct)
4. MMMM — Defines Month in word full(eg: October)
5. dd — Defines Day of month in number(eg: 23)
6. EEE — Defines Day of week in word short(eg: Thu)
7. EEEE — Defines Day of week in word full (eg: Thursday)
8. HH — Defines hrs of time in 24 hrs format(eg: 23:)
9. mm — Defines minutes of time(eg: :30)
10. HH: mm — Defines hrs and minutes in 24 hrs format(eg: 23: 30)
11. hh:mm — Defines hrs and minutes in 12 hrs format(eg: 11:30)
12. ss — Defines seconds of time
13. hh:mm:ss — Defines time with hrs, minutes and seconds(eg: 11:30:21)
14. a — Defines AM/PM format of time
15. hh:mm:ss a — Eg(11:30:21 PM)

Date Strings to a Date and vice versa:

First initialise Date formatter. Then give string date format to date format of date formatter instance. Then using date from string built in method of date formatter with user defined format we can pass user defined string date as param.

yyyy-MM-dd: Date String to Date and vice versa

var dateFormatter = DateFormatter()
dateFormatter.dateFormat = “yyyy-MM-dd”
let date = dateFormatter.date(from: dateString)
print(date!)
print(dateFormatter.string(from: date!))

output
2021–04–22 18:30:00 +0000 //date from string
2021–04–23 // again string from date

dd-MM-yyyy: Date String to Date

let dateString1 = “03–04–2021”
var dateFormatter1 = DateFormatter()
dateFormatter1.dateFormat = “dd-MM-yyyy”
let date1 = dateFormatter1.date(from: dateString1)
print(date1!)
print(dateFormatter1.string(from: date1!))

output
2021–04–02 18:30:00 +0000 // date from string
03–04–2021 // again string from date

EEE, dd MMM yyyy: Date and day from date string

let dateString2 = “Thu, 22 October 2015”
var dateFormatter2 = DateFormatter()
dateFormatter2.dateFormat = “EEE, dd MMM yyyy”
let date2 = dateFormatter2.date(from: dateString2)
print(date2!)
print(dateFormatter2.string(from: date2!))

output
2015–10–21 18:30:00 +0000//date from string
Thu, 22 Oct 2015 // again string from date

let dateObj = dateFormatter2.date(from: dateString2)
dateFormatter2.dateFormat = “MM-dd-yyyy”
print(dateFormatter2.string(from: dateObj!))

output
10–22–2015//date from string

Day string from Date String

let df = DateFormatter()
df.dateFormat = “YYYY-MM-dd”
let date3 = df.date(from: dateString)! //”2021–04–23" — Mentioned above
df.dateFormat = “EEEE”
print(df.string(from: date3))

output
Friday //Day of the given date

Day string, Month String from Date String

let df1 = DateFormatter()
df1.dateFormat = “YYYY-MM-dd”
let date4 = df1.date(from: dateString)!//”2021–04–23" — Mentioned above
df1.dateFormat = “EEEE, YYYY MMM dd”
print(df1.string(from: date4))

output
Friday, 2021 Apr 23 //Day of the given date

Current Time and date to string

let today = Date()
let formatter1 = DateFormatter()
formatter1.dateFormat = “HH:mm E, d MMM y”
print(formatter1.string(from: today))

output:
00:29 Thu, 15 Apr 2021//Gives curennt Date and time in specified format

BONUS😊

Date styles is a built-in method in date formatters. We will see here how those methods reacts with dates.

dateStyle: .long

let today1 = Date()
let formatter2 = DateFormatter()
formatter2.dateStyle = .long
print(formatter2.string(from: today1))

output
April 15, 2021 //long style date

dateStyle: .medium

let today2 = Date()
let formatter3 = DateFormatter()
formatter3.dateStyle = .medium
print(formatter3.string(from: today2))

output
Apr 15, 2021

dateStyle: .medium

let today3 = Date()
let formatter4 = DateFormatter()
formatter4.dateStyle = .short
print(formatter4.string(from: today2))

output
4/15/21

BONUS 2😊

iOS 13 introduce new class called RelativeDateTimeFormatter(). This formatter gives chat date formatter for the given date string or date. Below is the little example for that.

func chatDateFormat() -> String {
let formatter = RelativeDateTimeFormatter()
formatter.unitsStyle = .full
return formatter.localizedString(for: date1!, relativeTo: Date())
}

output
calling timeAgoDisplay()
Result: 1 week ago

Enjoy each and every line of coding. Hope this content will gives you a little bit clarity in how to use date formatters. Feel free to add comments here.

Happy Coding❤️