Swift with Copilot: What Day Is Today?

Date() is "now." Convert to a weekday name with DateFormatter (EEEE for full, EEE for abbreviated). Or use Calendar.current.component(.weekday, from:) for the integer.

A practical exercise. Date formatting in Swift is verbose; once you've seen it, the pattern is clear.

The Copilot prompt

// Print what day of the week today is
import Foundation

Copilot completes:

import Foundation

let formatter = DateFormatter()
formatter.dateFormat = "EEEE"
let today = formatter.string(from: Date())
print("Today is \(today)")
// Today is Wednesday

Walkthrough

Date() — current instant

let now = Date()
print(now)
// 2026-05-08 16:32:14 +0000

Date is a moment in time, internally a Double (seconds from Apple's reference date). It's not bound to a calendar or time zone — those come in when you format it.

DateFormatter

let formatter = DateFormatter()
formatter.dateFormat = "EEEE"          // full weekday name
let weekday = formatter.string(from: Date())
// "Wednesday"

dateFormat is a Unicode date pattern. Common tokens:

formatter.dateFormat = "yyyy-MM-dd"
formatter.string(from: Date())
// "2026-05-08"

Locale-aware

formatter.locale = Locale(identifier: "fr_FR")
formatter.dateFormat = "EEEE"
formatter.string(from: Date())
// "mercredi"

For user-facing strings, set the locale (or use the user's default). For machine-readable formats (logs, IDs), use Locale(identifier: "en_US_POSIX") to get a stable English format regardless of user settings.

Better: dateStyle and timeStyle

For locale-correct formatting, prefer dateStyle:

let f = DateFormatter()
f.dateStyle = .full      // "Wednesday, May 8, 2026"
f.dateStyle = .long      // "May 8, 2026"
f.dateStyle = .medium    // "May 8, 2026"
f.dateStyle = .short     // "5/8/26"

f.string(from: Date())

For just weekday, you'd combine:

f.dateStyle = .full
f.timeStyle = .none
// "Wednesday, May 8, 2026"

Then split the string. Or stick with dateFormat = "EEEE" for raw weekday only.

Modern alternative: Date.FormatStyle (iOS 15+)

let weekday = Date().formatted(.dateTime.weekday(.wide))
// "Wednesday"

let date = Date().formatted(.dateTime.year().month().day())
// "May 8, 2026"

let custom = Date().formatted(
  .dateTime.weekday(.wide).month(.wide).day().year()
)

Date.FormatStyle is the new, type-safe API. Each component is a method that returns a chainable style. Available on iOS 15+, macOS 12+.

For older deployment targets, stick with DateFormatter.

Calendar component access

If you want the integer weekday (1-7):

let weekday = Calendar.current.component(.weekday, from: Date())
print(weekday)
// 4 (Sunday=1, Saturday=7 in Gregorian)

Calendar.current is the user's calendar (usually Gregorian). component(_:from:) extracts:

• .year, .month, .day, .hour, .minute, .second
• .weekday, .weekOfYear, .weekOfMonth
• .dayOfYear, .quarter

let cal = Calendar.current
let now = Date()
print(cal.component(.year, from: now))    // 2026
print(cal.component(.month, from: now))   // 5
print(cal.component(.day, from: now))     // 8

To map weekday integer to name:

let formatter = DateFormatter()
let weekdays = formatter.standaloneWeekdaySymbols
// ["Sunday", "Monday", "Tuesday", ...]

let n = Calendar.current.component(.weekday, from: Date())
print(weekdays[n - 1])    // -1 because weekday is 1-indexed

Time zones

let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm zzz"
formatter.timeZone = TimeZone(identifier: "UTC")
formatter.string(from: Date())
// "2026-05-08 16:32 UTC"

formatter.timeZone = TimeZone(identifier: "America/New_York")
formatter.string(from: Date())
// "2026-05-08 12:32 EDT"

Default is the user's current time zone. For server-side or logging, use UTC explicitly.

Common stumbles

import Foundation missing. Date, DateFormatter, Calendar are in Foundation, not the Swift core. Required at the top.

weekday is 1-indexed. Sunday is 1, Saturday is 7. The standalone weekday symbol array is 0-indexed.

Mixing user locale and machine formats. For storage/JSON/logs: en_US_POSIX locale and ISO 8601 format. For UI: user's default locale.

Date arithmetic with seconds. Date(timeIntervalSinceNow: 86400) works for "tomorrow" most of the time. For DST-correct math, use Calendar.date(byAdding:value:to:).

Format string typos. mm is minutes, MM is months. hh is 12-hour, HH is 24-hour. Easy to mix up — read the table carefully.

Optional parsing. formatter.date(from: "bad") returns nil, not an error. Always handle the optional.

What's next

Episode 6: Exact day of 2023-01-02. Parsing a date string back into weekday.

Recap

Date() is now. DateFormatter with dateFormat = "EEEE" for weekday name. Locale matters — set en_US_POSIX for stable machine-readable, user's locale for UI. Calendar.current.component(.weekday, from:) for integer weekday. Modern API: Date().formatted(.dateTime.weekday(.wide)) (iOS 15+).

Next episode: parsing a date.