Batch Timestamp Converter

How the Batch Timestamp Converter works

Paste timestamps one per line and the browser parses each row locally. The tool recognizes Unix seconds, Unix milliseconds, ISO 8601/RFC 3339-style strings, and JavaScript-parseable date strings, then displays Unix seconds, milliseconds, ISO output, local time, UTC time, and relative age in one sortable table.

No timestamp list is uploaded to a backend service. The conversion uses JavaScript date parsing and formatting in the current page, so browser limits are the practical constraint for very large log extracts. For huge files, split the input into smaller batches and export CSV after each pass.

Format and timezone notes

• Seconds vs milliseconds: 10-digit Unix values are usually seconds; 13-digit values are usually milliseconds.
• Prefer timezone offsets: ISO strings with Z or an explicit offset avoid local-time ambiguity.
• Local display is contextual: local output uses the browser's configured timezone, not a remote geocoding or timezone API.
• Invalid rows are preserved: keep invalid rows visible when cleaning mixed log snippets so missing values are not silently lost.

Worked example

Paste 1717243200, 1717243200000, and 2024-06-01T12:00:00Z on separate lines. The first two represent the same instant when interpreted as seconds and milliseconds. The ISO row already carries its UTC marker, so it should align with the same UTC display if it represents that instant.

Sources

• MDN: JavaScript Date
• MDN: Date.parse()
• RFC 3339: Date and Time on the Internet

Example walk-through