How To Get The Difference Between Dates In Swift

Here are a couple of different ways to get the difference between dates in Swift.

Relative Difference Between Dates In Swift

If you want to create a string like “4 hours ago” or “5 months ago” and don’t want to specify the actual unit, it’s best to use RelativeDateTimeFormatter.

RelativeDateTimeFormatter was introduced in iOS 13 and uses the largest time measurement that makes sense.

Let’s take a look at some examples:

let exampleDate = Date().addingTimeInterval(-20000)
let formatter = RelativeDateTimeFormatter()
formatter.unitsStyle = .full
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())
print(relativeDate)

This above example will print:

5 hours ago

Let’s take a look at an example of a time in the future:

let exampleDate = Date().addingTimeInterval(100000)
let formatter = RelativeDateTimeFormatter()
formatter.unitsStyle = .full
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())
print(relativeDate)
in 1 day

RelativeDateTimeFormatter Unit Styles

You can use four different unit styles for the RelativeDateTimeFormatter:

Full

Full uses the full name of the date component:

formatter.unitsStyle = .full
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())
print(relativeDate)
// in 2 hours

Abbreviated

Abbreviated does what you would expect… uses an abbreviated version of the date component:

formatter.unitsStyle = .abbreviated
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())
print(relativeDate)
// in 2 hr.

If you want to get the difference in the dates in a more specific time unit, read on.

Short

In my testing, .short is generally the same as .abbreviated:

formatter.unitsStyle = .short
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())
print(relativeDate)
// in 2 hr.

Spell Out

Spell out replaces the number with a string:

formatter.unitsStyle = .spellOut
let relativeDate = formatter.localizedString(for: exampleDate, relativeTo: Date())
print(relativeDate)
// in two hours

Difference Between Dates In Days, Minutes, Seconds In Swift

What if you want to get difference between dates in days, minutes and seconds?

You can use this Date extension function to get that done:

extension Date {
  func offset(from date: Date) -> String {

    let dayHourMinuteSecond: Set<Calendar.Component> = [.day, .hour, .minute, .second]
    let difference = NSCalendar.current.dateComponents(dayHourMinuteSecond, from: date, to: self)

    let seconds = "\(difference.second ?? 0)s"
    let minutes = "\(difference.minute ?? 0)m" + " " + seconds
    let hours = "\(difference.hour ?? 0)h" + " " + minutes
    let days = "\(difference.day ?? 0)d" + " " + hours

    if let day = difference.day, day          > 0 { return days }
    if let hour = difference.hour, hour       > 0 { return hours }
    if let minute = difference.minute, minute > 0 { return minutes }
    if let second = difference.second, second > 0 { return seconds }
    return ""
  }
}

Here’s an example on how to use this function:

let date1 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 05, day: 20, hour: 5, minute: 45).date!
let difference = date2.offset(from: date1)
print(difference) // 140d 5h 45m 0s

Difference Between Dates In Seconds In Swift

Let’s create an extension to calculate the difference between dates in seconds:

extension Date {
  func seconds(from date: Date) -> Int {
    return Calendar.current.dateComponents([.second], from: date, to: self).second ?? 0
  }
}

Here’s an example using this new extension method:

let date1 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 01, day: 20, hour: 0, minute: 0).date!
let seconds = date2.seconds(from: date1)
print(seconds) // 1641600

Difference Between Dates In Minutes In Swift

To calculate the difference between dates in minutes, use this Date extension function:

extension Date {
  func minutes(from date: Date) -> Int {
      return Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
  }
}

Now here’s an example using this method:

let date1 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 01, day: 20, hour: 0, minute: 0).date!
let minutes = date2.minutes(from: date1)
print(minutes) // 27360

Difference Between Dates In Hours In Swift

To calculate the difference between dates in hours use this Date extension function:

extension Date {
  func hours(from date: Date) -> Int {
      return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
  }
}

Now here’s an example using this method:

let date1 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 20, minute: 0).date!
let hours = date2.hours(from: date1)
print(hours) // 20

Difference Between Dates In Days In Swift

To get the difference between dates in days, create this extension function for the Date class:

extension Date {
  func days(from date: Date) -> Int {
      return Calendar.current.dateComponents([.day], from: date, to: self).day ?? 0
  }
}

Here is an example of using this extension to get the days between dates in Swift:

let date1 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 01, day: 20, hour: 0, minute: 0).date!
let days = date2.days(from: date1)
print(days) // 19

Difference Between Dates In Weeks In Swift

To get the difference in weeks between dates in Swift, create this Date class extension:

extension Date {
  func weeks(from date: Date) -> Int {
      return Calendar.current.dateComponents([.weekOfMonth], from: date, to: self).weekOfMonth ?? 0
  }
}

Here’s how to use this extension:

let date1 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 01, day: 20, hour: 0, minute: 0).date!
let weeks = date2.weeks(from: date1)
print(weeks) // 2

Note that this does not count fractional or partial weeks! Here’s a solution that returns both weeks and days.

Difference Between Dates In Months In Swift

Create this Date class extension to get the difference in months:

extension Date {
  func months(from date: Date) -> Int {
    return Calendar.current.dateComponents([.month], from: date, to: self).month ?? 0
  }
}

Here’s how to use this extension:

let date1 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 10, day: 01, hour: 0, minute: 0).date!
let months = date2.months(from: date1)
print(months) // 9

Difference Between Dates In Years In Swift

Create this Date class extension to get the difference in months:

extension Date {
  func years(from date: Date) -> Int {
    return Calendar.current.dateComponents([.year], from: date, to: self).year ?? 0
  }
}

Here’s how to use this extension:

let date1 = DateComponents(calendar: .current, year: 2010, month: 01, day: 01, hour: 0, minute: 0).date!
let date2 = DateComponents(calendar: .current, year: 2020, month: 01, day: 01, hour: 0, minute: 0).date!
let years = date2.years(from: date1)
print(years) // 10
If you liked this post and want to learn more, check out The Complete iOS Developer Bootcamp. Speed up your learning curve - hundreds of students have already joined. Thanks for reading!

Eddy Chung

I teach iOS development on ZeroToAppStore.com.

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