How to format a date

Short answer

Create a DateTimeFormatter with a pattern and pass it to format():

void main() {
    var date = LocalDate.of(2026, 3, 8);
    var formatter = DateTimeFormatter.ofPattern("dd.MM.yyyy");
 
    IO.println(date.format(formatter));
}

Output:

08.03.2026

Pattern letters

yyyy is the year, MM the month as a number, MMM/MMMM the month name, dd the day, HH hours (0–23), mm minutes, ss seconds, EEEE the day of the week:

void main() {
    var dateTime = LocalDateTime.of(2026, 3, 8, 14, 5, 9);
 
    IO.println(dateTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
    IO.println(dateTime.format(DateTimeFormatter.ofPattern("EEEE, d MMMM yyyy", Locale.ENGLISH)));
}

Output:

2026-03-08 14:05:09
Sunday, 8 March 2026

In another language

Month and day names depend on the locale:

void main() {
    var date = LocalDate.of(2026, 3, 8);
 
    IO.println(date.format(DateTimeFormatter.ofPattern("d MMMM yyyy", Locale.GERMAN)));
    IO.println(date.format(DateTimeFormatter.ofPattern("d MMMM yyyy", Locale.of("ru"))));
}

Output:

8 März 2026
8 марта 2026

Built-in formats

ofLocalizedDate() picks the format used in a country:

void main() {
    var date = LocalDate.of(2026, 3, 8);
    var style = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM);
 
    IO.println(date.format(style.withLocale(Locale.US)));
    IO.println(date.format(style.withLocale(Locale.UK)));
    IO.println(date.format(DateTimeFormatter.ISO_DATE));
}

Output:

Mar 8, 2026
8 Mar 2026
2026-03-08

Common mistake

Mixing up letter case. MM is the month, mm minutes; YYYY is the "week-based year", which can differ from the regular year at the end of December:

void main() {
    var dateTime = LocalDateTime.of(2025, 12, 29, 10, 45);
 
    IO.println(dateTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
    IO.println(dateTime.format(DateTimeFormatter.ofPattern("YYYY-mm-dd", Locale.UK)));
}

Output:

2025-12-29
2026-45-29

In the second line both the year is wrong and minutes appear instead of the month.

Thanks for reading!

Short answer

Pattern letters

In another language

Built-in formats

Common mistake

Functions used in this recipe

Thanks for reading!