Is my data sent to a server?

No. Timestamp Converter runs entirely in your browser — the conversion is JavaScript's own Date and Intl objects plus a small parser of our own, and nothing you paste ever leaves the tab. That is why it keeps working offline once the page has loaded.

How does it know if a number is seconds or milliseconds?

By magnitude. A genuine Unix-seconds value stays below 1,000,000,000,000 all the way out to the year 33658; a millisecond value crosses that threshold around September 2001. Anything at or above it is read as milliseconds, anything below it as seconds — the same heuristic most date libraries use — and the report always states both readings so you can confirm it guessed right.

Why does To Timestamp only accept ISO 8601 or RFC 2822?

Because every other common date format is ambiguous about which number is the day and which is the month — 08/08/2026 reads one way in the US and another almost everywhere else, and guessing would produce a wrong answer that looks right. ISO 8601 (2026-08-08T12:00:00Z) and RFC 2822 (Sat, 08 Aug 2026 12:00:00 GMT) are both unambiguous by construction, so this tool accepts only those two rather than silently picking an interpretation for anything else.

What precision does this support?

Millisecond precision — the ceiling JavaScript's own Date object supports. An ISO 8601 input with finer-grained fractional seconds (microseconds or nanoseconds) is rounded to the nearest millisecond, and the report says so whenever that rounding actually happens.

What does the timezone option change?

Only the one localized line in the report. Unix seconds, Unix milliseconds, the ISO 8601 value, RFC 2822 and the day of week are all reported in UTC regardless — an instant in time is the same instant everywhere, and keeping those fields fixed to UTC is what makes the report unambiguous to read or paste into a log.

Does an ISO 8601 date need a time zone?

Only if it includes a time. A date on its own (2026-08-08) is always read as UTC midnight, which is unambiguous. A date with a time (2026-08-08T12:00:00) needs a Z or an offset like +02:00 — without one, that exact string means a different instant depending on which timezone reads it, so it's rejected rather than guessed at.

Conversion toolkitFreeFastPopular

Timestamp Converter

Convert a Unix timestamp to a readable date, or a date back to a timestamp — with the day of week, a chosen timezone and relative time, entirely in your browser.

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In-browserprocessing
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Conversion toolkit

Timestamp Converter

Timezone

Input

Output

The conversion report appears here as you type.

Ln 1, Col 1

Waiting for input

Paste, upload or type to begin.

Shortcuts⇧⌘CCopy output⌘LClear input

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Built for people who value their time

Every converters tool is fast, private and genuinely free — no dark patterns, no surprises.

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Jobs run on dedicated workers and finish in seconds — no queue, no spinner you can go make coffee to.

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Everything you upload is erased the moment the job finishes. Nothing is written to long-term storage, so there is no retention period to wait out.

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Desktop, tablet or phone, any modern browser. Nothing to install, no plugins, no extensions.

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Drop in a folder's worth of files and run the whole set through one tool in a single pass.

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Encrypted in transit, never used to train models, never sold. Many tools never send the file at all.

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How it works

Timestamp Converter in three steps

No account, no installation, no manual. It takes about as long to do as it does to read.

01
Paste a timestamp or a date
Unix seconds, Unix milliseconds, an ISO 8601 date, or an RFC 2822 date — the direction picks which one is expected.
02
Pick a direction and a timezone
To Date reads a timestamp; To Timestamp reads a date. The timezone only changes the one localized line in the report — everything else stays UTC.
03
Copy the report
Unix seconds, milliseconds, ISO 8601, RFC 2822, the day of week and a relative reading, all at once.

Questions

Frequently asked questions

Everything worth knowing before you run your first Timestamp Converter job. Still stuck? Talk to support.

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Guides and walkthroughs for getting more out of Timestamp Converter.

How Kalyvor keeps your files private

Encryption in transit, immediate deletion and what browser-side processing actually means.

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Batch processing: run 100 files at once

A practical walkthrough of queueing large jobs without babysitting the tab.

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Choosing the right tool for the job

A short decision guide for when two tools look like they do the same thing.

5 min read

Getting started with Kalyvor

From first upload to finished download in under a minute — the whole flow.

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Timestamp Converter

Timestamp Converter

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Built for people who value their time

Fast cloud processing

Auto file deletion

Works everywhere

Batch processing

Privacy first

No installation

Timestamp Converter in three steps

Paste a timestamp or a date

Pick a direction and a timezone

Copy the report

Frequently asked questions

Helpful articles

How Kalyvor keeps your files private

Batch processing: run 100 files at once

Choosing the right tool for the job

Getting started with Kalyvor

Explore more Developer tools