Swift:
Calculating a date in the future or past

How to:

Swift makes date math straightforward with Calendar and DateComponents. Here’s the gist:

import Foundation

// Today's date
let today = Date()

// Get the user's current calendar
let currentCalendar = Calendar.current

// Add 2 weeks to today
if let twoWeeksLater = currentCalendar.date(byAdding: .weekOfYear, value: 2, to: today) {
    print("Two weeks from now: \(twoWeeksLater)")
}

// Subtract 30 days from today
if let thirtyDaysBefore = currentCalendar.date(byAdding: .day, value: -30, to: today) {
    print("Thirty days ago: \(thirtyDaysBefore)")
}

Output could be like:

Two weeks from now: 2023-04-14 10:26:47 +0000
Thirty days ago: 2023-03-15 10:26:47 +0000

Remember, the actual output will vary since Date() gives you the current date and time.

Deep Dive

Before Swift, Objective-C and its clunkier syntax reigned. Swift’s Date, Calendar, and DateComponents simplify date operations. These objects respect time zones, handle daylight saving changes, and account for the user’s calendar settings – factors that were a slog to manage in Objective-C.

Alternatives include third-party libraries like SwiftDate, which can provide even more convenience and functionality. But for most, Swift’s built-in tools work just fine.

Dates are complex. They’re not just numbers to increase or decrease; they involve calendars, locale specificities, and time zones. Apple’s Foundation framework tackles this complexity, making sure your future and past date calculations make sense worldwide.