Can I use a DateComponentsFormatter to render the time of day?

Question

I would like to store a time of day in a simple way. For the purposes of my app, I only care about a specific time of day, like 2:30pm or 1:10am.

Using a DateComponentsFormatter I can get really close.

import Foundation

let formatter = DateComponentsFormatter()
formatter.unitsStyle = .positional
formatter.allowedUnits = [
    .hour,
    .minute
]
 
// Use the configured formatter to generate the string.
let timeAmount = 9000.0
let outputString = formatter.string(from: timeAmount)
let desiredString = "2:30 pm"import Foundation

let formatter = DateComponentsFormatter()
formatter.unitsStyle = .positional
formatter.allowedUnits = [
    .hour,
    .minute
]
 
// Use the configured formatter to generate the string.
let timeAmount = 9000.0
let outputString = formatter.string(from: timeAmount) // yields "2:30"
let desiredString = "2:30 pm"

Now, it seems that the formatter is really just saying "two hours and thirty minutes," so maybe I am barking up the wrong tree here. Does DateComponentsFormatter support my use case?

Answer 1

The DateComponentsFormatter is for expressing the amount of time between two dates. DateFormatter is for formatting dates or times. Use DateFormatter.

If your intent is to display a time in the UI, use DateFormatter, but

• Do not use dateFormat, but rather use timeStyle;
• Do not override locale;
• Do not set timeZone;

E.g. to show the current time in the UI:

let date = Date()
let formatter = DateFormatter()
formatter.timeStyle = .short
let string = formatter.string(from: date)

By the way, this will format time strings as preferred by the user (e.g. AM/PM for some of us, but in other locales, users may prefer 24 hour clock representation). When displaying information in the UI, we should always honor the user’s preferences.

---

If you’re trying to convert your 9,000 seconds to 2:30am:

let startOfDay = Calendar.current.startOfDay(for: Date())
let date = startOfDay.addingTimeInterval(9000)

let formatter = DateFormatter()
formatter.timeStyle = .short
let string = formatter.string(from: date)    // 2:30 AM

Clearly, if you happen to be on a date where you are shifting to or from daylight savings, your result may vary.