Formatting Relative Time in Swift: Quick Guide

In Swift, there are several ways to work with date formatting, such as DateComponentsFormatter and RelativeDateTimeFormatter.

DateComponentsFormatter

• Formats a time interval (duration) between two points in time.
• It doesn’t know whether it’s past or future, only the length of time.
• Example outputs: 2d, 1 hour, 5 minutes, 3h 15m
• Use it for: durations, timers, countdowns, video lengths, etc.

RelativeDateTimeFormatter

• Formats a date relative to another date, automatically handling past or future.
• Adds natural language like “ago” or “in”.
• Example outputs: 2 days ago, in 3 hours, yesterday, tomorrow
• Use it for: human-readable time expressions like “5m ago” or “in 2d”.

Quick Comparison

Purpose	Formatter	Example
Duration (no direction)	DateComponentsFormatter	2d, 3h 15m
Relative time (with context)	RelativeDateTimeFormatter	2 days ago, in 3 hours

Example of usage

DateComponentsFormatter:

private var abbreviatedFormatter: DateComponentsFormatter {
    let formatter = DateComponentsFormatter()
    formatter.allowedUnits = [.minute, .hour, .day]
    formatter.unitsStyle = .abbreviated
    formatter.maximumUnitCount = 1
    return formatter
}

func asAbbreviatedString() -> String {
    let from = Date().timeIntervalSince(self)
    return abbreviatedFormatter.string(from: from) ?? ""
}

RelativeDateTimeFormatter:

private var shortFormatter: RelativeDateTimeFormatter {
    let formatter = RelativeDateTimeFormatter()
    formatter.unitsStyle = .full
    return formatter
}

func asShortString() -> String {
    return shortFormatter.localizedString(for: self, relativeTo: Date())
}

Pro tip

Create an extension and add these shorthand functions to it.

extension Date {

    private var abbreviatedFormatter: DateComponentsFormatter {
        let formatter = DateComponentsFormatter()
        formatter.allowedUnits = [.minute, .hour, .day]
        formatter.unitsStyle = .abbreviated
        formatter.maximumUnitCount = 1
        return formatter
    }

    private var shortFormatter: RelativeDateTimeFormatter {
        let formatter = RelativeDateTimeFormatter()
        formatter.unitsStyle = .full
        return formatter
    }

    func asAbbreviatedString() -> String {
        let from = Date().timeIntervalSince(self)
        return abbreviatedFormatter.string(from: from) ?? ""
    }

    func asShortString() -> String {
        return shortFormatter.localizedString(for: self, relativeTo: Date())
    }
}