What This Calculator Does
This timestamp converter translates between Unix epoch timestamps and human-readable dates. In "Timestamp to Date" mode, you enter a Unix timestamp (seconds since January 1, 1970 UTC) and get the corresponding date, time, and ISO 8601 representation. In "Date to Timestamp" mode, you enter a date and time and receive the Unix timestamp in both seconds and milliseconds.
Inputs Explained
- Unix Timestamp (Timestamp to Date mode): An integer representing the number of seconds elapsed since January 1, 1970 00:00:00 UTC (the Unix epoch). Example: 1672531200 represents January 1, 2023.
- Date & Time (Date to Timestamp mode): A human-readable date and time input in your local datetime format.
How It Works
Unix time is a system for tracking time as a running total of seconds from a fixed point: midnight UTC on January 1, 1970, known as the Unix epoch. This system is used extensively in programming, databases, APIs, and file systems. The converter applies simple multiplication (seconds × 1000 for milliseconds) and JavaScript's built-in Date object to translate between the two representations.
Formulas Used
Date = Unix Epoch + (Timestamp × 1 second)
Timestamp (seconds) = (Date − Unix Epoch) ÷ 1 second
Timestamp (milliseconds) = Timestamp (seconds) × 1000
Timestamp (seconds) = (Date − Unix Epoch) ÷ 1 second
Timestamp (milliseconds) = Timestamp (seconds) × 1000
Timestamp Converter
Step-by-Step Example: Timestamp to Date
Input Timestamp: 1769904000
Step 1: Start from January 1, 1970 00:00:00 UTC.
Step 2: Add 1,769,904,000 seconds.
Result: February 1, 2026 00:00:00 UTC. ISO 8601: 2026-02-01T00:00:00.000Z.
Step-by-Step Example: Date to Timestamp
Input Date: January 31, 2026, 12:00:00 PM local time
Step 1: Convert to UTC based on local timezone offset.
Step 2: Calculate seconds since the Unix epoch.
Result: Unix timestamp depends on your local time zone offset.
Use Cases
- Software development: Debug timestamps in log files, database records, or API responses.
- System administration: Interpret file modification times or cron job schedules stored as epoch values.
- Data analysis: Convert timestamp columns in CSV files to human-readable dates for reporting.
- API testing: Generate or verify timestamp parameters when testing REST or GraphQL endpoints.
- Digital forensics: Interpret timestamps from file metadata, browser histories, or system logs.
Assumptions and Limitations
- Unix timestamps are integers representing seconds since Jan 1, 1970 UTC. Negative values represent dates before the epoch.
- The converter distinguishes between seconds (10-digit) and milliseconds (13-digit) timestamps automatically.
- JavaScript's Date object can represent dates from April 20, 271821 BCE to September 13, 275760 CE.
- Leap seconds are not represented in Unix time — the Unix clock does not count leap seconds.
- The "Date to Timestamp" mode uses your browser's local time zone unless otherwise specified.
Frequently Asked Questions
A Unix timestamp, also called epoch time or POSIX time, is a single integer that represents a specific moment in time. It counts the number of seconds that have elapsed since January 1, 1970 at 00:00:00 UTC, known as the Unix epoch. This system was introduced with the Unix operating system and is now used universally in programming, databases, and web APIs.
The Unix epoch is the fixed reference point for Unix timestamps: midnight UTC on January 1, 1970 (1970-01-01T00:00:00Z). All Unix timestamps are calculated as the number of seconds before or after this moment. The epoch was chosen arbitrarily when Unix was being developed at Bell Labs in the early 1970s.
A 13-digit timestamp is in milliseconds rather than seconds. To convert it, you can enter it directly — most modern timestamp tools, including this one, detect the length and handle it appropriately. To convert manually, divide by 1000 to get the seconds-based timestamp, then convert that to a date.
No. Unix time deliberately ignores leap seconds. Each day is treated as exactly 86,400 seconds regardless of whether a leap second was inserted. This means Unix timestamps can differ from UTC by up to the accumulated number of leap seconds (about 27 as of 2025), but for most practical purposes this is negligible.
Yes. A negative Unix timestamp represents a date before the epoch (January 1, 1970). For example, timestamp -86400 corresponds to December 31, 1969 00:00:00 UTC. Most modern programming languages and this converter handle negative timestamps correctly.
The Year 2038 problem affects systems that store Unix timestamps as signed 32-bit integers. The maximum value (2,147,483,647) corresponds to January 19, 2038 at 03:14:07 UTC. After this point, a 32-bit counter would overflow and wrap to a negative number. Modern 64-bit systems and this converter are not affected, as 64-bit timestamps can represent dates billions of years into the future.
ISO 8601 is an international standard for representing dates and times. The most common format looks like 2026-01-31T15:30:00Z where T separates date from time and Z indicates UTC. This converter displays the ISO 8601 representation alongside the human-readable date for easy copying into technical systems.
Unix timestamps are timezone-independent integers that sort naturally, compare easily, and avoid ambiguity. Date strings like '01/02/2026' could mean January 2 or February 1 depending on locale. Timestamps eliminate this confusion and are more efficient for storage and computation in databases and APIs.
Sources and References
- The Open Group Base Specifications – Unix Time — Official POSIX specification defining Unix epoch time and the seconds-since-epoch convention.
- RFC 3339 – Date and Time on the Internet — IETF standard for timestamps on the internet, closely related to ISO 8601.
- ISO 8601 Date and Time Format — The international standard for date and time representation.
- MDN Web Docs – JavaScript Date — Reference for JavaScript's Date object used in the conversion logic.
- Schema.org FAQPage Specification — Structured data standard for the FAQ markup on this page.