Scala Date FAQ: How do I format dates (DateTimeFormatter, LocalDate) in Scala?

Scala date FAQ: How do I format dates (DateTimeFormatter, LocalDate) in Scala? That is, when using Scala (2 or 3), how do I format dates, such as for printing them out in a desired format?

Solution: Scala date formatting

The solution is to use the java.time.format.DateTimeFormatter class. It provides three types of formatters for printing date/time values:

• Predefined formatters
• Locale formatters
• The ability to create your own custom formatters

Predefined formatters

DateTimeFormatter provides fifteen predefined formatters you can use. This example shows how to use a formatter with a LocalDate:

import java.time.LocalDate
import java.time.format.DateTimeFormatter
val d = LocalDate.now   // 2021-02-04

val f = DateTimeFormatter.BASIC_ISO_DATE
f.format(d)             // 20210204

These examples show what the other date formatters look like:

ISO_LOCAL_DATE     // 2021-02-04
ISO_DATE           // 2021-02-04
BASIC_ISO_DATE     // 20210204
ISO_ORDINAL_DATE   // 2021-035
ISO_WEEK_DATE      // 2021-W05-4

Locale formatters

Create locale formatters using these static DateTimeFormatter methods:

• ofLocalizedDate
• ofLocalizedTime
• ofLocalizedDateTime

You also apply one of four java.time.format.FormatStyle values when creating a localized date:

• SHORT
• MEDIUM
• LONG
• FULL

This example demonstrates how to use ofLocalizedDate with a LocalDate and FormatStyle.FULL:

import java.time.LocalDate
import java.time.format.{DateTimeFormatter, FormatStyle}

val d = LocalDate.of(2021, 1, 1)
val f = DateTimeFormatter.ofLocalizedDate(FormatStyle.FULL)
f.format(d)   // Friday, January 1, 2021

Using the same technique, this is what the four format styles look like:

SHORT    // 1/1/21
MEDIUM   // Jan 1, 2021
LONG     // January 1, 2021
FULL     // Friday, January 1, 2021

Custom patterns with ofPattern

You can also create custom patterns by specifying your own formatting strings. Here’s an example of the technique:

import java.time.LocalDate
import java.time.format.DateTimeFormatter

val d = LocalDate.now  // 2021-01-01
val f = DateTimeFormatter.ofPattern("yyyy-MM-dd")
f.format(d)            // 2021-01-01

Here are a few other common patterns:

"MM/dd/yyyy"       // 01/01/2021
"MMM dd, yyyy"     // Jan 01, 2021
"E, MMM dd yyyy"   // Fri, Jan 01 2021

This example demonstrates how to format a LocalTime:

import java.time.LocalTime
import java.time.format.DateTimeFormatter

val t = LocalTime.now
val f1 = DateTimeFormatter.ofPattern("h:mm a")
f1.format(t)   // 6:48 PM

val f2 = DateTimeFormatter.ofPattern("HH:mm:ss a")
f2.format(t)   // 18:48:33 PM

With a LocalDateTime you can format both date and time output:

import java.time.LocalDateTime
import java.time.format.DateTimeFormatter

val t = LocalDateTime.now
val f = DateTimeFormatter.ofPattern("MMM dd, yyyy h:mm a")
f.format(t)   // Jan 01, 2021 6:48 PM

See the DateTimeFormatter class for a complete list of predefined formats and formatting pattern characters that are available.

Notes

This is an excerpt from the Scala Cookbook, 2nd Edition ^(#ad). This is Recipe 3.11, Formatting Dates in Scala. Because this solution depends on the Java API, it can also be used with Java, Kotlin, and other JVM-based languages.