Unix Timestamp Converter
Convert Unix epoch timestamps (seconds & milliseconds) to UTC and local human-readable date strings, and convert dates back to Unix epoch.
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Understanding Unix Epoch Time
Unix time (also known as Epoch time or POSIX time) is a system for describing a point in time. It is defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970, minus leap seconds. Epoch time is used extensively in operating systems, databases, logging frameworks, and network protocols.
Seconds vs. Milliseconds
Traditional Unix timestamps in C, Python, and SQL databases measure elapsed time in seconds (10-digit integers). However, modern JavaScript (Date.now()), Java (System.currentTimeMillis()), and high-precision APIs use milliseconds (13-digit integers). FreeFileTool automatically detects 13-digit inputs and normalizes them for accurate conversion.
The Year 2038 Problem (Y2K38)
The Year 2038 problem affects programs that store Unix timestamps as 32-bit signed integers. At 03:14:07 UTC on 19 January 2038, the integer value reaches its maximum limit of 2,147,483,647. The next second overflows into negative numbers (-2,147,483,648), causing affected software to interpret the date as 13 December 1901. Modern 64-bit systems extend the limit by over 290 billion years.
Timezone Independence
A Unix timestamp is identical regardless of where you are located on Earth. 1700000000 represents the exact same absolute instant whether accessed from Tokyo, London, or San Francisco. The local human date display simply formats that universal instant according to your web browser's active timezone settings.
Frequently Asked Questions
What is a Unix timestamp?
A Unix timestamp (also known as Epoch time or POSIX time) is the total number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970, excluding leap seconds.
How do I know if a timestamp is in seconds or milliseconds?
Timestamps in seconds currently have 10 digits (e.g. 1700000000), whereas timestamps in milliseconds have 13 digits (e.g. 1700000000000). Our tool automatically detects 13-digit millisecond inputs.
What is the Year 2038 problem (Y2K38)?
On January 19, 2038, 32-bit signed integers will overflow beyond 2,147,483,647 seconds. Modern 64-bit systems and JavaScript's 64-bit numbers completely resolve this limit.
Are timezone offsets included in Unix timestamps?
No. Unix timestamps are strictly based on UTC (Coordinated Universal Time) regardless of your geographical location or daylight saving time adjustments.