◷Free
Julian day converter
Convert UTC timestamps and astronomical Julian dates (noon-based); numeric Julian results use 12 significant digits.
Julian day is Unix milliseconds divided by 86,400,000 plus 2,440,587.5; modified Julian day subtracts 2,400,000.5. The reference 2000-01-01 at 12:00 UTC is Julian day 2,451,545.
How to use
- Enter your text, values, or image.
- Adjust the options and run the tool.
- Copy or download your result.
Worked example
Example input
Conversion direction: to ISO timestamp: 2000-01-01T12:00:00Z Julian day: 2451545
Example result
{
"julianDay": 2451545,
"modifiedJulianDay": 51544.5,
"iso": "2000-01-01T12:00:00.000Z"
}Limitations and details
Julian input is rounded to milliseconds and results must be in years 0001–9999; this is astronomical Julian day, not a Julian-calendar date.
Inputs and options
- Conversion direction
- ISO to Julian day / Julian day to ISO
- ISO timestamp
- Text
- Julian day
- Number
Frequently asked questions
Is this tool free and private?
Yes. All 300 tools are free in this phase. Processing happens in your browser; your input and files are not sent to our servers.