15+ format conversions — free, private, browser-based

Convert Between Time Formats

Translate between Unix timestamps, ISO 8601, RFC 3339, RFC 2822, UTC and local date formats. The most-used pairs are listed below, or pick a tool to get started.

Popular Conversions

Supported Formats

Format	Example	Precision
Unix Seconds	1700000000	Seconds
Unix Milliseconds	1700000000123	Milliseconds
ISO 8601	2023-11-14T22:13:20Z	Seconds
RFC 3339	2023-11-14T22:13:20.000Z	Seconds
UTC Date	Tue, 14 Nov 2023 22:13:20 GMT	Seconds
Local Date	2023-11-14 22:13	Minutes

All Conversion Tools

Unix Timestamp ConverterTurn a Unix timestamp into UTC, local time and ISO 8601.
Epoch ConverterSee epoch seconds and milliseconds side by side, with UTC and local time.
Timestamp to DateReadable date, weekday, day of year and ISO week from a timestamp.
Date to TimestampConvert a date, time and time zone into a Unix timestamp.
Current Unix TimestampLive Unix time in seconds and milliseconds. Copy, pause or refresh.
Milliseconds to DateConvert Unix milliseconds, such as Date.now() values, to a date.
ISO 8601 to UnixTurn an ISO 8601 date-time string into a Unix timestamp.
Unix to ISO 8601Get an ISO 8601 string in UTC or with your local offset.
UTC ConverterConvert between local time and UTC in any time zone.
Epoch Milliseconds ConverterEpoch milliseconds to a readable date, in UTC, local time and ISO 8601.
Date Format ConverterOne date in, every common format out: ISO 8601, RFC 2822, RFC 3339, Unix and more.
ISO 8601 ConverterISO 8601 to Unix time and back, in one combined tool.
RFC 3339 ConverterRFC 3339 to Unix time and back, the strict internet date-time format.

Why Use Castov?

Free

Every tool is free to use, with no usage limits and no paid tier.

Fast

Small pages and almost no JavaScript, so results appear the moment you press Convert.

Private

The converters run in your browser, so what you type stays on your device. The few tools that use our servers, such as Env Vault, say so on their page.

Frequently Asked Questions

Is Castov really free?

Yes. All tools are free, with no account and no usage limits. The site may show ads in the future to cover running costs.

Is my data sent to a server?

Time, date and converter tools do not upload your input to Castov servers. Some preferences, such as theme, custom time zones and selected models, are stored locally on your device. Some features use the network by design: Env Vault uploads an encrypted copy, and P2P tools use public signaling servers.

What is a Unix timestamp?

A Unix timestamp is the number of seconds since 1 January 1970 at 00:00:00 UTC. It identifies one moment in time regardless of time zone, which is why programs and APIs use it.

Should I use seconds or milliseconds?

Use whichever your system produces. A 10-digit value is in seconds and a 13-digit value is in milliseconds. The converters can detect the unit for you.

Which time zones are supported?

All IANA time zones supported by your browser, such as America/New_York, Europe/Paris, Africa/Algiers and Asia/Tokyo, with daylight saving time rules applied for the date you choose.

Ready to convert a timestamp?

Pick any format pair above, or use the Unix Timestamp Converter for the most common case.

Unix Timestamp Converter ISO 8601 Converter