Unix Timestamp Converter: Complete Guide for Developers

• UTC-Based: Timestamps are always in UTC, making them timezone-independent.
• Numeric Format: Represented as a single number, easy to store and compare.
• Precise: Can represent exact moments in time down to the second or millisecond.
• Universal: Standard format used across programming languages and systems.
• Efficient: Compact representation that's efficient for databases and APIs.

• 0: January 1, 1970, 00:00:00 UTC (Unix epoch start)
• 1609459200: January 1, 2021, 00:00:00 UTC (in seconds)
• 1609459200000: January 1, 2021, 00:00:00 UTC (in milliseconds)
• 1735689600: January 1, 2025, 00:00:00 UTC (in seconds)

JavaScript:

// Convert seconds timestamp to date
const timestamp = 1609459200;
const date = new Date(timestamp * 1000);
console.log(date.toISOString()); // 2021-01-01T00:00:00.000Z

// Convert milliseconds timestamp to date
const msTimestamp = 1609459200000;
const date2 = new Date(msTimestamp);
console.log(date2.toISOString()); // 2021-01-01T00:00:00.000Z

Python:

from datetime import datetime

# Convert seconds timestamp to date
timestamp = 1609459200
date = datetime.fromtimestamp(timestamp)
print(date.isoformat())  # 2021-01-01T00:00:00

# Convert milliseconds timestamp to date
ms_timestamp = 1609459200000
date2 = datetime.fromtimestamp(ms_timestamp / 1000)
print(date2.isoformat())  # 2021-01-01T00:00:00

JavaScript:

// Convert date to seconds timestamp
const date = new Date('2021-01-01T00:00:00Z');
const timestampSeconds = Math.floor(date.getTime() / 1000);
console.log(timestampSeconds); // 1609459200

// Convert date to milliseconds timestamp
const timestampMs = date.getTime();
console.log(timestampMs); // 1609459200000

// Get current timestamp
const nowSeconds = Math.floor(Date.now() / 1000);
const nowMs = Date.now();

Python:

from datetime import datetime
import time

# Convert date to seconds timestamp
date = datetime(2021, 1, 1, 0, 0, 0)
timestamp = int(date.timestamp())
print(timestamp)  # 1609459200

# Get current timestamp
current_timestamp = int(time.time())
print(current_timestamp)

• UTC (Coordinated Universal Time): The standard time reference. Unix timestamps are always in UTC.
• Local Time: Time in your specific timezone. Our converter shows both UTC and local time.
• Conversion: The same timestamp represents the same moment globally, but displays differently in each timezone.

Timestamp: 1609459200

UTC: January 1, 2021, 00:00:00

EST (UTC-5): December 31, 2020, 19:00:00

JST (UTC+9): January 1, 2021, 09:00:00

All represent the same moment in time, just displayed in different timezones.

• Format: Integer number of seconds since epoch (e.g., 1609459200)
• Precision: Accurate to the second
• Common Use: Unix systems, many APIs, databases
• Range: Can represent dates from 1970 to beyond 2100

• Format: Integer number of milliseconds since epoch (e.g., 1609459200000)
• Precision: Accurate to the millisecond
• Common Use: JavaScript Date.now(), many modern APIs, high-precision timing
• Range: Same range as seconds but with millisecond precision

• Store in UTC: Always store timestamps in UTC. Convert to local time only for display to users.
• Be Consistent: Use the same timestamp format (seconds or milliseconds) throughout your application.
• Handle Both Formats: When working with APIs, be prepared to handle both seconds and milliseconds formats.
• Validate Input: Check that timestamps are within valid ranges and handle edge cases like negative timestamps.
• Use Libraries: For complex date operations, use established libraries like moment.js, date-fns, or Python's datetime.
• Consider Precision: Use milliseconds when you need sub-second precision, seconds when second-level precision is sufficient.
• Document Format: Document whether your API uses seconds or milliseconds to avoid confusion.
• Test Edge Cases: Test with timestamps at epoch (0), negative values, and very large values to ensure proper handling.
• Handle Expiration: When working with JWTs or session tokens, always check expiration timestamps before using them.