What Exactly is Epoch Time?
If you've ever worked with dates and times in programming, you've likely encountered Unix timestamps. But what are they really, and why do we use them?
Unix epoch time (also called Unix time, POSIX time, or simply "epoch") represents a single moment in time as the number of seconds that have passed since January 1, 1970, at midnight UTC (Universal Coordinated Time). This specific moment is known as "the Unix epoch" or "epoch zero."
Why January 1, 1970?
This date might seem arbitrary, but it was chosen when Unix was being developed in the early 1970s at Bell Labs. The developers needed a consistent starting point for their time-tracking system, and January 1, 1970, was close to when they were working on the project. It's become the universal standard ever since.
Understanding the Format
Unix timestamps come in different formats depending on the precision needed:
- Seconds (10 digits): The standard format, like
1728773400 - Milliseconds (13 digits): For more precision, like
1728773400000 - Microseconds (16 digits): For ultra-precise timing, like
1728773400000000
Common Time Intervals in Seconds
Understanding these common intervals can help you work with timestamps more intuitively:
| Time Period | Seconds | Quick Calculation |
|---|---|---|
| 1 Hour | 3,600 | 60 × 60 |
| 1 Day | 86,400 | 24 × 3,600 |
| 1 Week | 604,800 | 7 × 86,400 |
| 1 Month (avg) | 2,629,743 | 30.44 × 86,400 |
| 1 Year (avg) | 31,556,926 | 365.24 × 86,400 |
The Year 2038 Problem (Y2038)
Here's something important: many systems store Unix timestamps as a 32-bit signed integer. This creates a problem similar to the Y2K bug.
A 32-bit signed integer can only count up to 2,147,483,647 seconds. Once we hit January 19, 2038, at 03:14:07 UTC, this counter will overflow and wrap around to a negative number, potentially causing system failures and bugs.
Getting Current Epoch Time
Every programming language has its own way to retrieve the current Unix timestamp. Here are the most common methods:
Web Development
JavaScript
// Get timestamp in milliseconds, divide by 1000 for seconds
const timestamp = Math.floor(Date.now() / 1000);
// Alternative method
const timestamp = Math.floor(new Date().getTime() / 1000);PHP
// Simple and straightforward
$timestamp = time();
// Using DateTime (more flexible)
$timestamp = (new DateTime())->getTimestamp();Backend Languages
Python
import time
# Get current timestamp
timestamp = int(time.time())
# Using datetime module
from datetime import datetime
timestamp = int(datetime.now().timestamp())Java
// Returns milliseconds, divide by 1000 for seconds
long timestamp = System.currentTimeMillis() / 1000;
// Using Instant (Java 8+)
long timestamp = Instant.now().getEpochSecond();C#
// .NET Framework 4.6+ / .NET Core
long timestamp = DateTimeOffset.Now.ToUnixTimeSeconds();
// Older versions
var epoch = (DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalSeconds;Ruby
# Get current timestamp
timestamp = Time.now.to_i
# Alternative
timestamp = Time.new.to_iGo
import "time"
// Get current Unix timestamp
timestamp := time.Now().Unix()
// For milliseconds
milliseconds := time.Now().UnixMilli()Database Queries
MySQL
-- Get current timestamp
SELECT UNIX_TIMESTAMP();
-- Get timestamp from specific date
SELECT UNIX_TIMESTAMP('2025-10-12 14:30:00');PostgreSQL
-- Get current timestamp
SELECT EXTRACT(EPOCH FROM NOW());
-- From specific date
SELECT EXTRACT(EPOCH FROM TIMESTAMP '2025-10-12 14:30:00');SQLite
-- Get current timestamp
SELECT STRFTIME('%s', 'now');
-- From specific date
SELECT STRFTIME('%s', '2025-10-12 14:30:00');Command Line
Unix/Linux Shell
# Get current timestamp
date +%s
# Convert specific date to timestamp
date +%s -d "2025-10-12 14:30:00"
# For UTC/GMT time, use -ud instead of -d
date +%s -ud "2025-10-12 14:30:00"PowerShell
# Get current timestamp
[int][double]::Parse((Get-Date (Get-Date).ToUniversalTime() -UFormat %s))Converting FROM Epoch to Human-Readable Date
Once you have a Unix timestamp, you'll often need to convert it back to a readable date format:
JavaScript
// Convert timestamp to Date object
const date = new Date(timestamp * 1000); // Multiply by 1000 for milliseconds
// Format it
console.log(date.toLocaleString()); // Local format
console.log(date.toISOString()); // ISO 8601 formatPHP
// Format timestamp
$date = date('Y-m-d H:i:s', $timestamp);
// RFC 2822 format
$date = date('r', $timestamp);
// Using DateTime
$date = (new DateTime())->setTimestamp($timestamp)->format('Y-m-d H:i:s');Python
from datetime import datetime
# Convert to datetime object
dt = datetime.fromtimestamp(timestamp)
# Format it
formatted = dt.strftime('%Y-%m-%d %H:%M:%S')
# For UTC
dt_utc = datetime.utcfromtimestamp(timestamp)MySQL
-- Convert timestamp to datetime
SELECT FROM_UNIXTIME(1728773400);
-- With custom format
SELECT FROM_UNIXTIME(1728773400, '%Y-%m-%d %H:%i:%s');Converting FROM Human-Readable Date to Epoch
The opposite operation is equally important:
JavaScript
// Parse date string to timestamp
const timestamp = Math.floor(new Date('2025-10-12 14:30:00').getTime() / 1000);
// Using Date.parse()
const timestamp = Math.floor(Date.parse('October 12, 2025') / 1000);PHP
// Parse most English date texts
$timestamp = strtotime('15 November 2025');
$timestamp = strtotime('next Monday');
$timestamp = strtotime('+1 week');
// Using DateTime
$timestamp = (new DateTime('2025-10-12 14:30:00'))->getTimestamp();Python
from datetime import datetime
import time
# Parse date string
dt = datetime.strptime('2025-10-12 14:30:00', '%Y-%m-%d %H:%M:%S')
timestamp = int(dt.timestamp())
# For UTC
import calendar
timestamp = calendar.timegm(time.strptime('2025-10-12 14:30:00', '%Y-%m-%d %H:%M:%S'))Best Practices
When working with Unix timestamps in your applications:
- Always use 64-bit integers to avoid the Y2038 problem
- Store timestamps in UTC in your database, convert to local time only for display
- Be consistent with your precision (seconds vs milliseconds) throughout your application
- Document your format – make it clear whether you're using seconds or milliseconds
- Consider timezone-aware libraries for complex date/time operations
- Never store local time as a timestamp without timezone information
Conclusion
Unix timestamps are a fundamental concept in programming that every developer should understand. They provide a simple, universal way to represent time that works across all systems and programming languages.
Whether you're building a web application, working with databases, or just need to schedule tasks, understanding epoch time will make your life much easier. Use our Unix Timestamp Converter tool to quickly convert between timestamps and human-readable dates!