儒略日期转换器
将日历日期/时间转换为儒略日期 (JD)、修正儒略日期 (MJD)、儒略日数 (JDN) 和Unix时间 — 或将JD、MJD或Unix时间戳转换回日历日期。所有值均以UTC计算。将输入留空以使用当前时间。
输入
除非您添加偏移量 (例如 +02:00 或 Z)，否则解析为UTC。仅日期被视为 00:00 UTC。留空以使用当前时间。
输出
| 属性 | 值 |
|---|---|
| No data yet | |
使用指南
The Julian Date Converter turns a calendar date/time into a Julian Date (JD), Modified Julian Date (MJD) and integer Julian Day Number (JDN) — and converts any of those, or a Unix timestamp, straight back to a calendar date. Every representation is shown together, so there's no second lookup for the row you actually needed.
A Julian Date is a continuous count of days (and fractions of a day) since noon UTC on 1 January 4713 BC, used throughout astronomy and satellite/ephemeris work because it sidesteps calendars, months and leap years entirely — two instants just subtract into a day count. The Modified Julian Date (MJD = JD − 2400000.5) is the same idea with a more recent, shorter epoch (midnight UTC, 17 November 1858) and starts each day at midnight instead of noon.
How to use it
Pick a direction at the top:
- Date → Julian / Unix — type a date or date-time and read back its Julian Date, Modified Julian Date, Julian Day Number, and Unix timestamp (seconds and milliseconds), alongside ISO 8601 and RFC 7231 strings.
- Julian / Unix → Date — enter a number and choose what it represents (Interpret as: Julian Date, Modified Julian Date, Unix seconds, or Unix milliseconds) to get the calendar date, time and day of week it corresponds to — plus every other representation for the same instant.
Leave the input blank to convert the current time.
Why JD, MJD and JDN differ
- JD is a decimal day count that ticks over at noon UTC — so midnight UTC always lands on a
.5fraction (e.g.2460310.500000for 2024-01-01 00:00 UTC). - MJD is
JD − 2400000.5: the same count, re-anchored so it ticks over at midnight UTC instead — midnight UTC lands on a whole number (60310.000000for the same instant). - JDN is the plain integer day number (
floor(JD + 0.5)) — the value most "day since an epoch" catalogs (asteroid/comet designations, some satellite ephemerides) actually store.
Timezones and UTC
Every value is computed in UTC — Julian Date and Modified Julian Date have no timezone concept at all, so mixing in a local offset would make the result ambiguous. A date typed without an explicit offset is read as UTC; add a trailing Z or ±HH:MM if you mean a different zone.
What input formats are accepted?
For Date → Julian / Unix, the converter accepts ISO-style values: a bare date (2024-01-01), a date and time separated by a space or a T (2024-01-01 12:00:00 or 2024-01-01T12:00:00), optional fractional seconds, and an optional trailing Z or ±HH:MM offset.
For Julian / Unix → Date, enter any decimal number (Julian Date and Modified Julian Date are rarely whole numbers) and pick the matching unit from the dropdown.
Is my data sent anywhere?
No. The conversion runs entirely in your browser, so nothing you enter leaves your device.
Use it from code
From 3 credits per callREST API
curl -X POST https://api.iotools.cloud/v1/tool/julian-date-converter \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"direction": "to-julian",
"dateTime": "2000-01-01 12:00:00"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `julian-date-converter` tool (Julian Date Converter) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.