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Unix Timestamp Converter: Complete Guide to Converting Epoch Time

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Unix Timestamp Converter: Complete Guide to Converting Epoch Time

Unix timestamps (also called epoch time or POSIX time) are a fundamental concept in programming. They represent time as the number of seconds since January 1, 1970, 00:00:00 UTC.

What is a Unix Timestamp?

A Unix timestamp is a single integer that represents a specific moment in time:

1711084800  →  March 22, 2024 00:00:00 UTC
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Why use timestamps?

  • Universal: Works across all timezones and programming languages
  • Compact: Single number instead of complex date objects
  • Sortable: Chronological ordering is just numeric sorting
  • Math-friendly: Easy to calculate durations (subtraction)

Seconds vs Milliseconds

Different systems use different precision:

System Format Example
Unix/Linux Seconds 1711084800
JavaScript Milliseconds 1711084800000
Python Seconds (float) 1711084800.123
Java Milliseconds 1711084800000L

How to tell them apart:

  • Seconds: 10 digits (around 1-2 billion)
  • Milliseconds: 13 digits (around 1-2 trillion)

Converting Timestamp to Date

JavaScript 

const timestamp = 1711084800;
const date = new Date(timestamp * 1000); // Convert to milliseconds
console.log(date.toISOString()); // "2024-03-22T00:00:00.000Z"
console.log(date.toUTCString());  // "Fri, 22 Mar 2024 00:00:00 GMT"
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Python 

import datetime

timestamp = 1711084800
dt = datetime.datetime.fromtimestamp(timestamp, tz=datetime.timezone.utc)
print(dt.isoformat())  # "2024-03-22T00:00:00+00:00"
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PHP 

$timestamp = 1711084800;
echo date('Y-m-d H:i:s', $timestamp); // "2024-03-22 00:00:00"
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Converting Date to Timestamp

JavaScript 

const date = new Date('2024-03-22 12:00:00');
const timestamp = Math.floor(date.getTime() / 1000);
console.log(timestamp); // 1711108800
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Python 

import datetime

dt = datetime.datetime(2024, 3, 22, 12, 0, 0, tzinfo=datetime.timezone.utc)
timestamp = int(dt.timestamp())
print(timestamp)  # 1711108800
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Common Use Cases

1. API Rate Limiting 

const rateLimitReset = 1711090000; // Server response
const now = Math.floor(Date.now() / 1000);
const secondsUntilReset = rateLimitReset - now;
console.log(`Wait ${secondsUntilReset} seconds`);
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2. Session Expiry 

const sessionExpiry = Math.floor(Date.now() / 1000) + 3600; // Expires in 1 hour
localStorage.setItem('expiry', sessionExpiry);

// Later...
const expiry = parseInt(localStorage.getItem('expiry'));
if (Math.floor(Date.now() / 1000) > expiry) {
  console.log('Session expired');
}
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3. Database Timestamps 

-- SQLite example
CREATE TABLE events (
  id INTEGER PRIMARY KEY,
  created_at INTEGER DEFAULT (strftime('%s', 'now'))
);

-- Query events from last 24 hours
SELECT * FROM events
WHERE created_at > (strftime('%s', 'now') - 86400);
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Important Gotchas

Year 2038 Problem

32-bit signed integers can only store timestamps up to:

2,147,483,647 seconds = January 19, 2038, 03:14:07 UTC
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After this, 32-bit systems will overflow (similar to Y2K). Solution: Use 64-bit integers or switch to date objects.

Timezone Confusion 

// ❌ WRONG - Creates local time
const date = new Date('2024-03-22 12:00:00');

// ✅ CORRECT - Explicit UTC
const date = new Date('2024-03-22T12:00:00Z');
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Always be explicit about timezones when parsing dates!

Milliseconds Auto-Detection 

function smartTimestampConvert(timestamp) {
  // If > 10 billion, assume milliseconds
  if (timestamp > 10000000000) {
    timestamp = Math.floor(timestamp / 1000);
  }
  return new Date(timestamp * 1000);
}
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Try It Yourself

Use our free Unix Timestamp Converter to:

  • Convert timestamps to human-readable dates
  • Convert dates to Unix timestamps
  • Auto-detect seconds vs milliseconds
  • Support UTC and local timezones
  • Copy formatted outputs instantly

Quick Reference 

// Get current timestamp
Math.floor(Date.now() / 1000)

// Convert timestamp → date
new Date(timestamp * 1000)

// Convert date → timestamp
Math.floor(date.getTime() / 1000)

// Add 1 day to timestamp
timestamp + 86400

// Check if timestamp is in the past
timestamp < Math.floor(Date.now() / 1000)
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Conclusion

Unix timestamps are the universal language of time in programming. Master these conversions and you'll handle dates with confidence across any system.

Key Takeaways:

  • Timestamps = seconds since Jan 1, 1970 UTC
  • JavaScript uses milliseconds (×1000 larger)
  • Always specify timezones when parsing dates
  • Watch out for the Year 2038 problem on 32-bit systems

Need to convert timestamps right now? Try our free timestamp converter tool — no installation required!

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