How to convert milliseconds to "hh:mm:ss" format?

java

time-unit

date-formatting

java-8

byAlex Kataev·Jan 22, 2025

Here's a quick solution that utilizes SimpleDateFormat to convert milliseconds:

long ms = YOUR_MILLIS; // Don't forget to replace this with your actual milliseconds
String time = new SimpleDateFormat("HH:mm:ss").format(new Date(ms - TimeZone.getDefault().getRawOffset()));
// Bravo, time is now in "hh:mm:ss"

Note: make sure to subtract your timezone offset to display the accurate UTC time.

Breaking down the TimeUnit approach

Java's TimeUnit class lets you convert different units of time easily and concisely:

long milliseconds = 123456789; // Fantastic arbitrary number

// Hours - Spoiler Alert: It run in circles every 24 hours
long hours = TimeUnit.MILLISECONDS.toHours(milliseconds);
long remainingMsAfterHours = milliseconds - TimeUnit.HOURS.toMillis(hours);

// Minutes - Because being precisely on time is overrated
long minutes = TimeUnit.MILLISECONDS.toMinutes(remainingMsAfterHours);
long remainingMsAfterMinutes = remainingMsAfterMinutes - TimeUnit.MINUTES.toMillis(minutes);

// Seconds - for all our fellow procrastinators out there
final long seconds = TimeUnit.MILLISECONDS.toSeconds(remainingMsAfterMinutes) - (minutes * 60);

// Time's ready, serve hot!
String formattedTime = String.format("%02d:%02d:%02d", hours, minutes, seconds);

We use String.format to keep those leading zeroes in the "hh:mm:ss" format, because we like things neat, don't we?

Converting time the java.time way

Java 8 gifted us java.time, a more dependable way to handle time:

Instant epochInstant = Instant.ofEpochMilli(milliseconds);
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("HH:mm:ss")
                                               .withZone(ZoneId.of("UTC"));
String formatted = formatter.format(epochInstant);

Bring on edge cases like Daylight Saving Time or leap seconds, and java.time will laugh in their faces while producing reliable format.

Introduce some reusability

Create a generic method for this time formatting logic. Sharing is caring, after all!:

public static String formatMillisToHHMMSS(long ms) {
    long hours = TimeUnit.MILLISECONDS.toHours(ms);
    long minutes = TimeUnit.MILLISECONDS.toMinutes(ms) % 60;
    long seconds = TimeUnit.MILLISECONDS.toSeconds(ms) % 60;

    return String.format("%02d:%02d:%02d", hours, minutes, seconds);
}

For more complex scenarios, apache commons' DurationFormatUtils has got your back:

String formattedDuration = DurationFormatUtils.formatDuration(milliseconds, "HH:mm:ss,SSS");

**Fraction of seconds support? ** Check! Extremely helpful in high-precision circumstances.

Validate your masterpiece

Test your method against a spattering of scenarios because that's what robust code is all about:

long[] testMillis = {0, 1000, 123450, 3600000, 86399999}; // Check all: Zero, One-liners, Textwalls, and Full-length novels
for (long millis : testMillis) {
    System.out.println(formatMillisToHHMMSS(millis)); // Print and admire your handywork
}

This validation ensures your ultimate solution runs smoothly for all milliseconds!

A solution for every time (pun intended)

For the ones using older Java versions, never fear, SimpleDateFormat is here:

SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
sdf.setTimeZone(TimeZone.getTimeZone("UTC")); // Don't confuse the computer with different timezones
String formatted = sdf.format(new Date(milliseconds));