How do I know if my timestamp is in seconds or milliseconds?

A 10-digit number is almost certainly seconds. A 13-digit number is milliseconds. For example, 1700000000 is seconds (November 2023) while 1700000000000 is milliseconds representing the same moment.

What is the maximum Unix timestamp?

32-bit signed integers can hold timestamps up to 2147483647 (19 January 2038), the so-called Year 2038 problem. JavaScript uses 64-bit floats so this tool handles timestamps far beyond that date.

Timestamp Converter — Unix Timestamp to Date

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Current Unix timestamp (seconds)

Unix timestamp → human date

Date / time → Unix timestamp

About the Timestamp / Unix Time Converter

A Unix timestamp is the number of seconds elapsed since 00:00:00 UTC on 1 January 1970 — the Unix epoch. It is the standard time representation in databases, APIs, log files, and server-side code because it is a single integer: timezone-independent, sort-friendly, and easy to do arithmetic on. JavaScript uses millisecond timestamps (13 digits); most Unix systems use second-precision (10 digits).

Common timestamp formats

Unix seconds — 10-digit integer: 1748822400. Used in Unix systems, Python, and server logs.
Unix milliseconds — 13-digit integer: 1748822400000. Used in JavaScript Date.now(), Java, and many databases.
ISO 8601 — 2025-06-01T12:00:00Z. International standard for human-readable timestamps in REST APIs.
RFC 2822 — Mon, 01 Jun 2025 12:00:00 +0000. Used in email headers and HTTP Date headers.

The Year 2038 problem

32-bit signed integers overflow on 19 January 2038 at 03:14:07 UTC. Modern 64-bit systems extend the range to the year 292 billion. If you work with embedded systems or legacy 32-bit databases, this is a real concern to address before 2038.

Working with timestamps in different databases

Different databases store and query timestamps differently. PostgreSQL's TIMESTAMPTZ stores UTC and converts to session timezone for display. MySQL TIMESTAMP stores UTC (max value: 2038-01-19); DATETIME stores local time with no timezone awareness. MongoDB stores ISODate() values as 64-bit UTC milliseconds. Always use timezone-aware types in production.

PostgreSQL — use TIMESTAMPTZ (with time zone); avoid TIMESTAMP WITHOUT TIME ZONE for application data
MySQL — TIMESTAMP (stores UTC, max 2038) vs DATETIME (no timezone, max 9999)
SQLite — no native datetime type; store as ISO 8601 text or Unix integer
MongoDB — ISODate() is UTC milliseconds; always consistent regardless of server timezone

Frequently Asked Questions

What is a Unix timestamp?

A Unix timestamp is the number of seconds since 00:00:00 UTC on 1 January 1970. It is timezone-independent: the same integer represents the same moment everywhere. JavaScript uses milliseconds (multiply seconds by 1000); Python and most Unix tools use whole seconds.

How do I convert a Unix timestamp to a readable date?

JavaScript: new Date(timestamp * 1000).toISOString() (multiply by 1000 if the timestamp is in seconds). Python: from datetime import datetime; datetime.utcfromtimestamp(ts). Terminal: date -d @1748822400 (Linux) or date -r 1748822400 (Mac).

What is the difference between Unix seconds and milliseconds?

Both count from the same epoch (1 Jan 1970 UTC). Unix seconds is a 10-digit integer; Unix milliseconds is a 13-digit integer (multiply seconds by 1000). JavaScript Date.now() returns milliseconds. Python time.time() returns seconds as a float. Always verify which unit an API expects.

What is ISO 8601 format?

ISO 8601 is the international standard for dates and times: YYYY-MM-DDTHH:MM:SSZ where T separates date and time, and Z denotes UTC. Example: 2025-06-01T14:30:00Z. It is unambiguous, lexicographically sortable, and the recommended format for REST API responses and JSON payloads.

How do I get the current Unix timestamp?

JavaScript: Math.floor(Date.now() / 1000) for seconds, or Date.now() for milliseconds. Python: import time; int(time.time()). PHP: time(). Bash: date +%s. PostgreSQL: SELECT EXTRACT(EPOCH FROM NOW()).