Convert a Julian Day to a Date
Turn each Julian Day number back into a Gregorian calendar date (YYYY-MM-DD). Runs entirely in your browser, so your data never leaves your device.
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Output
The result appears here as you type.
How to use Convert a Julian Day to a Date
- 1. Paste your Julian Day numbers. Enter one Julian Day number per line. Each number is converted independently, so a batch of astronomical day counts processes in a single pass.
- 2. Read the converted calendar date. There are no options to configure. Each Julian Day number is converted back into a Gregorian calendar date in YYYY-MM-DD form.
- 3. Copy the calendar dates. Copy the resulting dates into your report, spreadsheet, or document wherever a human-readable calendar date is more useful than the raw astronomical day count.
When to use Convert a Julian Day to a Date
Convert a Julian Day to a Date turns the continuous Julian Day number back into an ordinary Gregorian calendar date. Use it whenever an astronomy calculation or dataset gives you a Julian Day figure that needs to be read as a real-world date.
- Reading an ephemeris table. An astronomy reference lists event times as Julian Day numbers, and converting them back to calendar dates makes the table understandable without a separate lookup.
- Interpreting a script's output. A Python or C astronomy script outputs results as Julian Day numbers, and converting the final figure back to a calendar date makes the result usable in a report.
- Double-checking a historical date calculation. A calculation involving the interval between two historical events produces a Julian Day result, and converting it back confirms the resulting date matches expectations.
Examples
The J2000.0 epoch
Input
2451545
Output
2000-01-01
Several Julian Days at once
Input
2440588 2461236
Output
1970-01-01 2026-07-14
About the Convert a Julian Day to a Date tool
Convert a Julian Day to a Date is a free online tool that works entirely inside your web browser. Turn each Julian Day number back into a Gregorian calendar date (YYYY-MM-DD). Because the processing happens on your own device, nothing you enter is uploaded, logged or stored anywhere.
This page is one of 90 Time utilities on EditSafely. Each one does a single job well, and all of them follow the same rule: your input stays on your machine.
There is nothing to configure. Provide the input and the result appears on its own. 2 worked examples further down the page show exactly what the tool produces for real inputs.
Because nothing leaves your device, the tool is suitable for sensitive content such as internal documents, credentials or customer data. It also responds instantly, since every keystroke is handled on your own machine rather than by a remote API.
Frequently asked questions
Does Convert a Julian Day to a Date cost anything?
Yes, it is completely free. All 2,658 tools on EditSafely work without an account, a subscription or usage limits.
Is it safe to paste sensitive or confidential data?
No data leaves your device. The whole tool is JavaScript that runs inside your browser tab, so there is no upload, no server-side processing and no log of what you did. If you disconnect from the internet after the page loads, it keeps working.
How much text can I process at once?
There is no fixed limit. Because the work happens on your own device rather than on a shared server, the practical ceiling is your machine's memory, which comfortably handles inputs far larger than typical online tools allow.
Do I need to sign up or install anything?
Nothing to install and no account needed. Open the page in any up-to-date browser, including on a phone or tablet, and the tool is ready.
How do I use the result?
The output panel has a one-click copy button, and you can keep refining the input while you work; the result updates in place as you type.
Related tools
All Time Tools →Convert a Date to a Julian Day
Turn each calendar date into its astronomical Julian Day number (days since 4713 BC).
Convert Julian Calendar to Gregorian Calendar
Restate each Old Style Julian calendar date as the equivalent modern Gregorian date.
Find the Day of the Week
Name the weekday for each calendar date you paste in.
Find the Difference Between Dates
Count the days between two calendar dates on each line (also shown broken down into years, months and days).