Unix time, also known as epoch time or POSIX time, is a system for describing instants in time. It represents the number of seconds (or milliseconds) that have elapsed since January 1, 1970, 00:00:00 UTC, excluding leap seconds. This moment is known as the Unix epoch.

Unix timestamps are widely used in programming, databases, APIs, system logs, and file systems because they provide a simple, timezone-independent way to represent dates and times. They're particularly useful for storing timestamps in databases, comparing dates, calculating durations, and working with APIs that require standardized time representations.

Unix timestamps can be represented in two formats:

• Seconds (10 digits): The number of seconds since the Unix epoch. Example: 1609459200 represents January 1, 2021, 00:00:00 UTC. Common in Unix systems, Python, and some APIs.
• Milliseconds (13 digits): The number of milliseconds since the Unix epoch. Example: 1609459200000 represents the same moment. Standard in JavaScript, Java, and many modern APIs.

One of the most common mistakes developers make is confusing seconds and milliseconds. If you treat a millisecond timestamp as seconds, your date jumps about 1000x into the future (tens of thousands of years). If you treat seconds as milliseconds, you will land near the Unix epoch. Our tool automatically detects whether your timestamp is in seconds or milliseconds based on its value, preventing this error.

Unix timestamps are timezone-independent - they represent the same moment in time regardless of timezone. However, when displaying or working with dates, timezone matters significantly:

• UTC vs Local Time: Always be aware of whether you're working with UTC or local time. Our tool displays both so you can see the difference.
• API Timestamps: Most APIs use UTC timestamps. When converting, ensure you're using the correct timezone.
• JWT Tokens: JWT tokens use Unix timestamps for exp (expiration) and iat (issued at) claims. These are always in seconds and represent UTC time.
• Database Storage: Store timestamps as Unix timestamps or UTC dates to avoid timezone confusion.
• Daylight Saving Time: Local time conversions can be affected by DST. UTC timestamps avoid this issue.

Our tool helps you avoid timezone pitfalls by showing both local time and UTC time side-by-side, making it easy to verify your conversions are correct regardless of your location.

• API Development: Converting API timestamps to readable dates for debugging and logging
• JWT Token Debugging: Decoding exp and iat claims in JWT tokens to verify expiration times
• Database Queries: Converting between Unix timestamps and human-readable dates for SQL queries
• Log Analysis: Converting Unix timestamps in log files to readable dates
• Date Calculations: Converting dates to timestamps for duration calculations and comparisons
• File Timestamps: Understanding file modification times in Unix systems
• API Testing: Generating timestamps for API requests and testing expiration logic
• Data Migration: Converting timestamps between different systems and formats

ISO 8601 is an international standard for date and time representation. It provides a clear, unambiguous way to represent dates and times. Our tool displays timestamps in ISO 8601 format (e.g., 2021-01-01T00:00:00.000Z), which is widely used in APIs, JSON data, and modern applications. ISO 8601 format is timezone-aware and provides a standard way to exchange date and time information between systems.

Our tool displays relative time (e.g., "2 hours ago", "in 3 days") next to the local time. This makes it easy to understand how recent or how far in the future a timestamp is. Relative time is particularly useful when debugging expiration times, checking token validity, or understanding log timestamps. The relative time is calculated when you convert or edit the input, giving you immediate context about the timestamp.

All timestamp conversions happen entirely in your browser using JavaScript. Your data never leaves your device, is never sent to any server, and is never stored. This privacy-first approach ensures that sensitive timestamps like authentication token expiration times, API keys, or system logs remain completely private and secure. Whether you're debugging JWT tokens, analyzing API responses, or converting database timestamps, your data stays local and secure.