Unix Timestamp Converter

Milestone Epoch Timestamps

Throughout computer history, key Unix timestamp milestones have marked major computational benchmarks and system transitions:

Seconds vs. Milliseconds & The Year 2038 Bug

A frequent source of software bugs is conflating epoch seconds with epochmilliseconds, or neglecting integer overflow thresholds:

• 10 Digits vs. 13 Digits: Standard POSIX/C timestamps use seconds (10 decimal digits in the contemporary era, e.g. 1,770,000,000). High-level runtimes like JavaScript (Date.now()) and Java (System.currentTimeMillis()) return milliseconds (13 decimal digits, e.g. 1,770,000,000,000). Treating a millisecond timestamp as seconds places the date hundreds of thousands of years in the future.
• 32-Bit Signed Integer Overflow: Traditional C/C++ runtimes allocate a signed 32-bit integer for time_t. The maximum positive value is 2^31 - 1 = 2,147,483,647. OnTuesday, January 19, 2038 at 03:14:07 UTC, incrementing by one second causes an arithmetic overflow to -2,147,483,648, wrapping the calendar back to December 13, 1901.
• Modern 64-Bit Resolution: Modern 64-bit operating systems, databases, and programming languages use 64-bit signed integers (time64_t), which can safely represent dates over 292 billion years into the future.
• Daylight Saving Time (DST) Nuances: Unix time itself is continuous, linear, and strictly independent of timezones or Daylight Saving Time adjustments. When local clocks spring forward or fall back, the underlying Unix epoch count continues unchanged; only the localized presentation string shifts.

POSIX Time & Technical Specifications

POSIX time is specified by IEEE Std 1003.1 / The Open Group relative to the Unix epoch (1970-01-01T00:00:00Z UTC). Its timestamp model does not assign a distinct representable timestamp to an inserted leap second:

• Leap Second Omission: POSIX timestamps treat ordinary days as 86,400 secondsand do not provide a unique timestamp value for the inserted leap second itself. How a system clock reconciles UTC leap-second adjustments—such as stepping, repeating a displayed second, or smearing—is implementation-specific. Therefore POSIX timestamp differences should not be interpreted as a perfect count of physical SI seconds across leap-second boundaries.

Retrieving Current Epoch in Major Languages

// Epoch seconds
const sec = Math.floor(Date.now() / 1000);

// Epoch milliseconds
const ms = Date.now();

import time

# Epoch seconds
sec = int(time.time())

# Epoch milliseconds
ms = int(time.time() * 1000)

import "time"

// Epoch seconds
sec := time.Now().Unix()

// Epoch milliseconds
ms := time.Now().UnixMilli()

-- PostgreSQL
SELECT EXTRACT(EPOCH FROM NOW())::BIGINT;

-- MySQL
SELECT UNIX_TIMESTAMP();

Time Resolution Precision Comparison

Client-Side Calculation Guarantee

Calculators and converters on EveryTools prioritize performance, privacy, and zero latency:

• Zero Network Latency: All conversions execute in single-digit milliseconds directly in your browser tab using native ECMAScript date calculations.
• Native Browser API Execution: All string parsing, arithmetic, and timezone formatting use the native Date and Intl.DateTimeFormat engines built into your browser.
• Local Processing Policy: Input values processed locally; analytics only fixed UI event identifiers. No timestamp, date string, or document metadata is transmitted to EveryTools servers.

Unix Timestamp FAQ