How do I tell if a timestamp is in seconds or milliseconds?

Seconds timestamps for dates after 2001 are 10 digits (≥ 1,000,000,000). Milliseconds timestamps are 13 digits (≥ 1,000,000,000,000). This tool auto-detects: any number larger than 10,000,000,000 is treated as milliseconds.

What timezone does the output use?

All output is in UTC. Unix timestamps have no timezone — they always count seconds from the UTC epoch. The ISO 8601 string ends with 'Z' (Zulu / UTC). To display in a local timezone, use your application's date-formatting library with a timezone identifier (e.g. 'America/New_York').

Are UUID v4 values truly random and safe to use as primary keys?

Yes. UUID v4 uses a cryptographically secure random number generator (Node.js crypto.randomUUID(), which calls the OS CSPRNG). Two independently generated v4 UUIDs colliding is astronomically unlikely — roughly a 1 in 5.3×10³⁶ chance per pair. They are safe as primary keys in databases, session tokens, and correlation IDs.

What is the difference between UUID v1, v4, and v7?

v1 encodes the MAC address and timestamp — sortable but exposes hardware identity. v4 is fully random — the most privacy-safe and widely supported. v7 (RFC 9562, 2024) encodes a millisecond-precision timestamp in the high bits so UUIDs sort chronologically, which improves database index locality. This tool generates v4. For v7, use a dedicated library like 'uuid' on npm.

Tool comparison

Unix Timestamp Converter vs UUID Generator

Unix Timestamp Converter (datetime) and UUID Generator (generation) come from different categories but appear together in developer workflows. This guide explains what each does and when to reach for one over the other.

Bottom line

Timestamp Converter reads or displays a specific point in time. UUID Generator mints identifiers that are globally unique, and some variants (UUIDv1, UUIDv7) encode the current timestamp inside the UUID itself. Use Timestamp Converter to inspect a moment in time; use UUID Generator to create new unique identifiers.

What each tool does

Unix Timestamp Converter

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970 — a moment known as the Unix epoch. Timestamps are the universal language of time in software: databases store them as integers, APIs return them in JSON, log files record them for every event, and JWT tokens use them for 'iat' (issued-at) and 'exp' (expiry) claims. Unlike formatted date strings, Unix timestamps are unambiguous — they have no timezone, no locale, and no format variation. JavaScript and many APIs also use millisecond timestamps (Unix seconds × 1000). This tool converts in both directions: paste a timestamp to get a human-readable date in UTC and ISO 8601, or paste a date string to get the corresponding epoch seconds and milliseconds.

Open Unix Timestamp Converter →

UUID Generator

A UUID (Universally Unique Identifier) is a 128-bit identifier standardised in RFC 4122 and represented as 32 hexadecimal digits in the pattern xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUID version 4 — the most common variant — fills all bits with cryptographically random data, making collisions statistically impossible: with 1 trillion UUIDs generated per second it would take approximately 85 years before a 50% chance of a single collision occurs. UUIDs are used as primary keys in databases, correlation IDs in distributed logs, session tokens, file names, API resource identifiers, and idempotency keys in payment systems. Because they are generated client-side without a central registry, distributed systems can create UUIDs in parallel without coordination. The compact format (no hyphens) saves 4 characters and is commonly used in URLs and file names.

Open UUID Generator →

Side-by-side comparison

Feature	Unix Timestamp Converter	UUID Generator
Category	datetime	generation
Primary purpose	Convert Unix timestamps to human-readable dates and ISO 8601, or convert dates back to epoch seconds.	Generate one or more cryptographically random UUID v4 identifiers instantly.
Inputs	input, mode	count, format, validate
Outputs	unix_seconds, unix_ms, iso8601, utc, relative, valid, error	uuids, count, format, is_valid, validated_version

When to use each

Use Unix Timestamp Converter when…

How to convert a Unix timestamp to a readable date

Turn an epoch seconds value from a database, API, or log file into a human-readable date.

How to convert a date to a Unix timestamp

Get the Unix epoch seconds for a specific date to use in a database, API, or JWT.

Use UUID Generator when…

How to generate a UUID v4 online

Get a cryptographically random UUID instantly without installing any tools.

How to validate whether a string is a valid UUID

Check if an ID from an API response or user input matches the UUID format.

Frequently asked questions

How do I tell if a timestamp is in seconds or milliseconds?: Seconds timestamps for dates after 2001 are 10 digits (≥ 1,000,000,000). Milliseconds timestamps are 13 digits (≥ 1,000,000,000,000). This tool auto-detects: any number larger than 10,000,000,000 is treated as milliseconds.
What timezone does the output use?: All output is in UTC. Unix timestamps have no timezone — they always count seconds from the UTC epoch. The ISO 8601 string ends with 'Z' (Zulu / UTC). To display in a local timezone, use your application's date-formatting library with a timezone identifier (e.g. 'America/New_York').
Are UUID v4 values truly random and safe to use as primary keys?: Yes. UUID v4 uses a cryptographically secure random number generator (Node.js crypto.randomUUID(), which calls the OS CSPRNG). Two independently generated v4 UUIDs colliding is astronomically unlikely — roughly a 1 in 5.3×10³⁶ chance per pair. They are safe as primary keys in databases, session tokens, and correlation IDs.
What is the difference between UUID v1, v4, and v7?: v1 encodes the MAC address and timestamp — sortable but exposes hardware identity. v4 is fully random — the most privacy-safe and widely supported. v7 (RFC 9562, 2024) encodes a millisecond-precision timestamp in the high bits so UUIDs sort chronologically, which improves database index locality. This tool generates v4. For v7, use a dedicated library like 'uuid' on npm.