> For the complete documentation index, see [llms.txt](https://docs.radiantdrift.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.radiantdrift.com/julian-day.md).

# Julian Day

{% hint style="info" %}
**All** input dates are assumed to be in the Gregorian calendar. Even if you provide a date earlier than the first adoption of the Gregorian calendar, it is taken as is and is **not** assumed to be a Julian calendar date.
{% endhint %}

### Calculate Julian Day

{% openapi src="<https://api.radiantdrift.com/openapi/0.18.3.json>" path="/julian-day/{date}" method="get" %}
<https://api.radiantdrift.com/openapi/0.18.3.json>
{% endopenapi %}

### Calculate Gregorian Date/Time

{% openapi src="<https://api.radiantdrift.com/openapi/0.18.3.json>" path="/date/{julian-day}" method="get" %}
<https://api.radiantdrift.com/openapi/0.18.3.json>
{% endopenapi %}