Date / DateFormatter / Calendar
Swift's Foundation framework provides Date, DateFormatter, and Calendar for working with dates and times — including formatting, parsing, and date arithmetic.
Class overview
| Class / Property | Description |
|---|---|
| Date() | Creates an object representing the current date and time. |
| DateFormatter | A class that converts between Date values and strings. |
| DateFormatter.dateFormat | Sets the format string for the date and time (e.g., yyyy/MM/dd). |
| DateFormatter.locale | Sets the locale used for formatting. |
| Calendar | Performs calendar calculations, retrieves date components, and adds or subtracts date values. |
| DateComponents | A structure that represents date and time components such as year, month, day, hour, minute, and second. |
| timeIntervalSince1970 | Returns the number of seconds elapsed since January 1, 1970 (Unix timestamp). |
Sample code
import Foundation
// Get the current date and time
let now = Date()
print("Now: \(now)")
// DateFormatter: convert between Date and String
let formatter = DateFormatter()
formatter.dateFormat = "yyyy/MM/dd HH:mm:ss"
formatter.locale = Locale(identifier: "en_US")
let dateString = formatter.string(from: now)
print("Formatted: \(dateString)")
// Parse a string into a Date
if let parsedDate = formatter.date(from: "2026/03/06 12:00:00") {
print("Parsed: \(parsedDate)")
}
// Calendar: extract date components
let calendar = Calendar.current
let components = calendar.dateComponents([.year, .month, .day, .hour], from: now)
print("Year: \(components.year!), Month: \(components.month!), Day: \(components.day!)")
// Calendar: add days to a date
var addComponents = DateComponents()
addComponents.day = 7 // 7 days later
if let nextWeek = calendar.date(byAdding: addComponents, to: now) {
print("One week later: \(formatter.string(from: nextWeek))")
}
// Compare two dates
let date1 = now
let date2 = calendar.date(byAdding: .hour, value: 3, to: now)!
print("date2 is after date1: \(date2 > date1)")
// Unix timestamp
print("Unix timestamp: \(Int(now.timeIntervalSince1970))")
Notes
Date stores time internally in UTC (Coordinated Universal Time). When displaying a date, use DateFormatter to apply the appropriate locale and time zone.
Creating a DateFormatter is expensive, so avoid instantiating it repeatedly. Reuse it via a static property or lazy var instead. The format string in dateFormat is case-sensitive. 'MM' means month; 'mm' means minute. An incorrect format string may cause the formatter to return nil.
For URL handling, see URL / URLComponents / URLSession.
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