JSON Date Converter
Paste any date value you found in a JSON API response - an ISO string, epoch timestamp, or .NET-style /Date()/ value - and instantly see it converted to every common format.
Recommended Settings
Pro Tips
- •This auto-detects the format - just paste the raw value exactly as it appeared in your JSON, no need to specify which format it is
- •A 10-digit or shorter all-numeric value is assumed to be seconds; anything longer is assumed to be milliseconds
- •The .NET /Date(1700000000000)/ format was common in older ASP.NET and WCF web services before ISO 8601 became standard
- •JSON itself has no native date type - APIs each pick their own convention, which is why this variety of formats exists
Most Popular
Most users paste an ISO 8601 string or a plain epoch number copied directly from an API response
When to Use This Tool
Quickly check what date and time a raw API response value actually represents.
Convert a date from one API's format into the format another system expects.
Decode the older .NET /Date()/ timestamp format still found in some legacy services.
Verify date handling is correct while building an integration between two systems.
How It Works
Check the pasted value against several common JSON date patterns - ISO 8601 strings, plain epoch numbers, and .NET's /Date()/ wrapper
Parse whichever pattern matches into a standard Unix millisecond timestamp
Display that moment in time in every other common format for easy comparison
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Client-side pattern-based date format detection for optimal performance on modern browsers.
Open Source
Built with verified, open-source libraries. Fully transparent.
Frequently Asked Questions
Why does JSON have so many different date formats?
JSON itself has no built-in date type - it's just numbers, strings, and objects - so different APIs and frameworks each adopted their own convention for representing dates as one of those basic types.
How does the tool know if a number is seconds or milliseconds?
It uses length as a heuristic - a 10-digit or shorter number is assumed to be seconds (since that covers dates up to the year 2286), while longer numbers are assumed to be milliseconds.
What is the .NET /Date()/ format?
It's a JSON date convention used by older Microsoft web service frameworks like ASP.NET AJAX and WCF, wrapping a millisecond epoch timestamp (and optional timezone offset) inside a string like /Date(1700000000000)/.
Is my data sent to a server?
No. All detection and conversion happens entirely in your browser.
What if my date format isn't recognized?
Try isolating just the date value itself without surrounding JSON punctuation - if it's still not recognized, it may use a less common custom format not covered by this tool.