Unix Timestamp Converter

What Is a Unix Timestamp?

A Unix timestamp — also called epoch time, POSIX time, or simply Unix time — is the number of seconds that have elapsed since January 1, 1970, 00:00:00 UTC, a moment known as the Unix epoch. It is one of the most widely used time representations in computing because it provides a single, timezone-independent integer that any system can unambiguously interpret.

For example, the timestamp 1700000000 corresponds to November 14, 2023, 22:13:20 UTC. Every second that passes increments this number by one. Negative values represent dates before 1970 — -86400, for instance, is December 31, 1969.

Why Do Developers Use Timestamps?

Timestamps solve a surprisingly tricky problem: reliably recording when something happened across different machines, programming languages, and time zones. Here is why they are the industry default:

• Timezone neutrality. A timestamp is always UTC. You never have to wonder whether a stored value is in EST, CET, or JST. The display layer converts to the user's locale; the storage layer stays clean.
• Trivial comparison and arithmetic. Because a timestamp is just a number, sorting events chronologically is a simple integer sort. Computing the duration between two events is subtraction. No date parsing libraries required.
• Language and database portability. Every major programming language — JavaScript, Python, Java, Go, Rust, C — has built-in functions to produce and consume Unix timestamps. Every major database stores them natively.
• Compact storage. A 32-bit integer takes 4 bytes; a 64-bit integer takes 8. Compare that to an ISO 8601 string (2024-01-15T12:00:00.000Z) at 24 bytes. At scale, the savings add up.

Timestamp Precision: Seconds, Milliseconds, and Microseconds

The original Unix clock ticks in seconds, producing 10-digit numbers (until November 2286). Over time, applications needed finer granularity:

• Seconds (s) — 10 digits. Used by most POSIX APIs, the time() system call, and many REST APIs.
• Milliseconds (ms) — 13 digits. JavaScript's Date.now() returns milliseconds. Java's System.currentTimeMillis() does the same. This is the most common web precision.
• Microseconds (μs) — 16 digits. Used in high-frequency trading, scientific instrumentation, and some databases like PostgreSQL's timestamptz.
• Nanoseconds (ns) — 19 digits. Go's time.Now().UnixNano() returns nanoseconds. Observability platforms like Jaeger and OpenTelemetry trace spans in nanoseconds.

This converter auto-detects whether your input is in seconds or milliseconds based on digit count (10 or fewer digits = seconds, 13 or more = milliseconds).

The Year 2038 Problem (Y2K38)

Many systems store Unix timestamps in a signed 32-bit integer. The maximum value of a signed 32-bit int is 2,147,483,647, which corresponds to January 19, 2038, 03:14:07 UTC. One second later, the counter overflows and wraps around to a large negative number — interpreted as December 13, 1901.

This is the Year 2038 problem, sometimes called Y2K38 or the "Epochalypse." It is the spiritual successor to the Y2K bug, and it is arguably more dangerous because timestamps are embedded far deeper in system infrastructure than two-digit year strings ever were.

The fix is straightforward: use a 64-bit integer. A signed 64-bit timestamp will not overflow for another 292 billion years. Most modern operating systems, databases, and programming languages have already migrated. However, embedded systems, legacy firmware, and some file formats (like ext3 inodes) still rely on 32-bit timestamps and will need updates before 2038.

Working with Timestamps in Different Languages

JavaScript / TypeScript

// Current timestamp in milliseconds
const ms = Date.now();

// Convert to seconds
const seconds = Math.floor(ms / 1000);

// From timestamp to Date
const date = new Date(1700000000 * 1000);

// From Date to ISO string
console.log(date.toISOString());
// "2023-11-14T22:13:20.000Z"

Python

import time
from datetime import datetime, timezone

# Current timestamp in seconds
ts = time.time()            # 1700000000.123456

# From timestamp to datetime
dt = datetime.fromtimestamp(1700000000, tz=timezone.utc)

# From datetime to ISO string
print(dt.isoformat())       # 2023-11-14T22:13:20+00:00

Java

import java.time.Instant;

// Current timestamp
Instant now = Instant.now();
long epochSecond = now.getEpochSecond();
long epochMilli  = now.toEpochMilli();

// From timestamp
Instant instant = Instant.ofEpochSecond(1700000000L);
System.out.println(instant);
// 2023-11-14T22:13:20Z

Go

package main

import (
    "fmt"
    "time"
)

func main() {
    // Current timestamp
    now := time.Now().Unix()      // seconds
    nowMs := time.Now().UnixMilli() // milliseconds

    // From timestamp
    t := time.Unix(1700000000, 0).UTC()
    fmt.Println(t.Format(time.RFC3339))
    // 2023-11-14T22:13:20Z
}

Bash / Shell

# Current timestamp
date +%s

# Convert timestamp to date (GNU date)
date -d @1700000000

# Convert timestamp to date (macOS)
date -r 1700000000

Common Timestamp Gotchas

• Mixing seconds and milliseconds. Passing a millisecond value to a function expecting seconds (or vice versa) produces dates thousands of years in the future or milliseconds after the epoch. Always check the expected unit in the API documentation.
• Floating-point timestamps. Some languages return timestamps as floats (Python's time.time()). Floating-point arithmetic can introduce rounding errors. Prefer integer milliseconds when sub-second precision matters.
• Leap seconds. Unix time does not account for leap seconds. UTC occasionally inserts a leap second to keep solar time and atomic time in sync. Unix timestamps simply repeat or skip that second, which means a Unix timestamp is not a perfectly monotonic count of SI seconds since the epoch.
• Negative timestamps. Dates before January 1, 1970 produce negative timestamps. Most modern systems handle them correctly, but some older parsers or databases may reject them.

Frequently Asked Questions

What is the Unix epoch?

The Unix epoch is January 1, 1970, 00:00:00 UTC. It was chosen as the reference point for Unix time when the system was being developed at Bell Labs in the early 1970s. All Unix timestamps are measured relative to this moment.

How do I get the current Unix timestamp?

In most languages: Date.now() (JavaScript, milliseconds), time.time() (Python, seconds), System.currentTimeMillis() (Java, milliseconds), time.Now().Unix() (Go, seconds). In a terminal, run date +%s.

Is Unix time the same as UTC?

Not exactly. Unix time is based on UTC but ignores leap seconds. In practice, the two are almost identical — they differ by at most a few seconds over decades. For most applications the distinction is irrelevant, but for scientific or astronomical computing it matters.

What happens after the year 2038?

Systems using signed 32-bit integers for timestamps will overflow on January 19, 2038. The solution is to use 64-bit integers, which modern systems already do. If you maintain legacy systems, audit your timestamp storage and plan a migration well before 2038.

Can I use this tool offline?

Yes. This tool runs entirely in your browser. No data is sent to any server. You can bookmark this page and use it without an internet connection (after the initial page load).

How accurate is the live timestamp display?

The live display updates every second using your device's system clock. Its accuracy depends on your operating system's time synchronization (typically NTP). For most purposes it is accurate to within a few milliseconds.