Unix Timestamp and Epoch in TypeScript

Unix time counts elapsed time from the Unix epoch at 1970-01-01T00:00:00Z. Different ecosystems use different units, so always label whether a value is in seconds, milliseconds, microseconds, or nanoseconds.

Quick Start#

The following example uses the standard TypeScript API or a widely used package for this task.

Quick start#

1const milliseconds: number = Date.now();2const seconds: number = Math.floor(milliseconds / );34const iso: string = new Date(milliseconds).toISOString();5console.log({ seconds, milliseconds, iso });

Common Operations#

This second pattern covers a common production operation or a safer way to handle real input.

Normalize seconds vs milliseconds#

1function toMilliseconds(value: number): number {2  return Math.abs(value) <  ? value *  : value;3}45const date = new Date(toMilliseconds(timestamp));

Important Notes#

Prefer explicit API field names such as createdAtMs or expiresAtSeconds rather than guessing the unit from magnitude whenever you control the contract.

Best Practices#

1. Treat external input as untrusted and handle parse/validation errors explicitly.
2. Keep encoding, units, formats, and library-specific mapping rules explicit at system boundaries.
3. Add test vectors that cover empty input, Unicode text, malformed input, and representative production data.

References#

• POSIX Seconds Since the Epoch
• TypeScript Handbook