Java DateTimeFormatter Pattern Reference

Java DateTimeFormatter

Java 8 introduced the java.time package with DateTimeFormatter as the modern replacement for the legacy SimpleDateFormat. It is thread-safe, immutable, and supports the same pattern letter conventions.

Pattern Letters

Letter	Meaning	Example
yyyy	Year (4-digit)	2026
yy	Year (2-digit)	26
MM	Month (zero-padded)	02
M	Month (no padding)	2
MMM	Abbreviated month	Feb
MMMM	Full month name	February
dd	Day (zero-padded)	28
d	Day (no padding)	28
EEEE	Full weekday	Saturday
EEE	Abbreviated weekday	Sat
HH	Hour 24h (zero-padded)	14
hh	Hour 12h (zero-padded)	02
mm	Minute	30
ss	Second	00
SSS	Millisecond	123
a	AM/PM	PM
XXX	Offset (+HH:MM or Z)	+09:00
VV	Timezone ID	Asia/Tokyo

Usage

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

LocalDateTime dt = LocalDateTime.of(2026, 2, 28, 14, 30, 0);
DateTimeFormatter fmt = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
String result = dt.format(fmt); // "2026-02-28 14:30:00"

// Parsing
LocalDateTime parsed = LocalDateTime.parse("2026-02-28 14:30:00", fmt);

Predefined Formatters

Java provides built-in formatters for common standards:

DateTimeFormatter.ISO_LOCAL_DATE       // 2026-02-28
DateTimeFormatter.ISO_LOCAL_DATE_TIME  // 2026-02-28T14:30:00
DateTimeFormatter.ISO_OFFSET_DATE_TIME // 2026-02-28T14:30:00+09:00
DateTimeFormatter.RFC_1123_DATE_TIME   // Sat, 28 Feb 2026 14:30:00 +0900

SimpleDateFormat Migration

Legacy code using SimpleDateFormat uses the same pattern letters but is not thread-safe. Migrate by replacing:

// Before (legacy, not thread-safe)
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

// After (modern, thread-safe)
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd");