Unix Timestamp Converter - Epoch Seconds, Milliseconds & ISO Dates
This Unix Timestamp Converter transforms epoch values into human-readable UTC and local dates, and converts ISO 8601 strings back to Unix seconds and milliseconds. Values below 1 trillion are treated as seconds; larger values as milliseconds - matching how most APIs and logs store time.
Converted values
Detected unit: milliseconds
Detection rule
Values below 1,000,000,000,000 are treated as seconds. Larger values are milliseconds - covering dates through year 2286 in seconds and far beyond in milliseconds.
Seconds vs milliseconds detection
APIs disagree on epoch units. PostgreSQL extract(epoch) returns seconds. JavaScript Date.now() returns milliseconds. MongoDB ObjectId timestamps embed seconds. When debugging, compare magnitude: if the number looks like 1704067200, it is seconds; if 1704067200000, milliseconds.
Click Use now to snapshot the current epoch in both units, or switch to Date → Epoch mode to paste an ISO string from JSON logs and recover the integer your backend stored.
Unix Timestamp FAQ
What is a Unix timestamp?
A Unix timestamp counts seconds (or sometimes milliseconds) since the Unix epoch: January 1, 1970 00:00:00 UTC. It is timezone-independent storage - the same integer represents one instant worldwide. JavaScript Date objects internally store milliseconds since that epoch, which is why JS APIs often return 13-digit values.
How do I tell if a timestamp is in seconds or milliseconds?
Check the digit count and magnitude. Current-era seconds timestamps have 10 digits (around 1.7 billion in 2026). Millisecond timestamps have 13 digits (around 1.7 trillion). A practical rule: values below 1,000,000,000,000 (1e12) are seconds; at or above are milliseconds. This tool applies that threshold automatically.
How do I convert Unix timestamp to a readable date?
Multiply seconds by 1000 (if needed) and pass the result to new Date() in JavaScript, or use date -d @TIMESTAMP on Linux. UTC output uses toISOString(). This converter shows ISO 8601 UTC, a human UTC string, your local timezone, and both second and millisecond forms so you can paste the format your stack expects.
What is the Unix timestamp for January 1, 2024?
Midnight UTC on 2024-01-01 is Unix second 1704067200 and millisecond 1704067200000. Always confirm whether your API expects seconds or milliseconds - mixing them is one of the most common timezone-adjacent bugs in web development.
Unix timestamp converter vs JavaScript Date.now(): which to use?
Date.now() returns current milliseconds in code running on your machine. This converter is for debugging API payloads, parsing log files, verifying database columns, and converting historical timestamps without writing a script - especially when you need UTC labels and ISO strings side by side.
Does daylight saving time affect Unix timestamps?
No. Unix timestamps are always UTC-based elapsed time. Local display may shift with DST when formatted in a regional timezone, but the underlying integer never changes. Store and transmit epoch values in UTC; convert to local time only at the presentation layer.
Sources & review
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