Written by Linh Vo
on February 01, 2017

Working with Dates in Swift

Date

A specific point in time, independent of any calendar or time zone.

The simplest way to get the current date is by:

let date = Date()
print(date) // prints 2017-02-01 10:48:09 +0000

This date object supports comparison, time interval calculation, and the creation of a new date relative to another date. For example:

let now = Date()
let hourAgo = now - 3600 // an hour is 3600 seconds
let timeInterval = now.timeIntervalSince(hourAgo)
print(timeInterval) // prints 3600, which is an hour in secs
print(now) // prints 2017-02-01 12:59:44 +0000
print(hourAgo) // prints 2017-02-01 11:59:44 +0000

This is already cool but if you need to have more control over the date you should use DateFormatter coming up next.

DateFormatter

If you want to show the date information in another format, e.g. to show the date in some different country’s style, then you need to use DateFormatter.

Date Formatting with Style Presets

DateFormatter provides you with a variety of different date formats you can utilize.

As an example, let’s create a DateFormatter object, and configure the dateStyle and timeStyle properties to change the style of the string representation of the date.

let date = Date() // The current date
let dateFormatter = DateFormatter()
dateFormatter.dateStyle = .full
dateFormatter.timeStyle = .full
let dateText = dateFormatter.string(from: date)
print(dateText)
// Prints:
// Saturday, February 01, 2017 at 10:44:34 AM Indochina Time

The complete list of all the possible style presets for dateStyle and timeStyle is .none, .short, .medium, .long, .full. Feel free to experiment with these.

DateFormat — Another Way to Customize Date Format

In addition to dateStyle and timeStyle, dateFormat is also a way to customize the date formatting. However, it should be used only when working with fixed format representations, such as ISO8601DateFormatter.

Also, it does not make sense to use the previously described dateStyle or timeStyle properties while using the dateFormat in the DateFormatter.

Date Style Customization + Localization

If the date format you prefer is not possible with the earlier style presets, you can use the setLocalizedDateFormatFromTemplate function in DateFormatter to achieve the style you are lacking with.

As an example, let’s say we want to show the current date in the Finnish calendar in a way it is shown in Finland, that is, for example 01.02.2017. This format is not plausible with the earlier style presets, so we need to customize the DateFormatter:

let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier:"fi_FI") // Date in Finland
dateFormatter.setLocalizedDateFormatFromTemplate("yyyy-MM-dd")
let dateStr = dateFormatter.string(from: Date())
print(dateStr) // prints 01.02.2017

Notice that we used a locale property of the DateFormatter. With locale the date format gets automatically converted to the format that is used in a specific country defined by the locale.

You should always call setLocalizedDateFormatFromTemplate only after setting the locale of the DateFormatter in order to show the correctly formatted date in the region.

DateComponents

DateComponents represents the date in the units of time. E.g. hours, minutes, seconds, etc. It lets you easily access and modify all the time components of the date separately.

In the following example, the current date is extracted to its time components using DateComponents.

let currentDate = Date()
let calendar = Calendar.current // The user's current calendar
let date = calendar.dateComponents(in: .current, from: currentDate)
let year = date.year
let month = date.month
let day = date.day
let hour = date.hour
let minute = date.minute
let second = date.second

Reference: Medium

← → Top