This page shows the current date and time using the systems implemented by the French First Republic. The calendar was used from 1793 to 1805 and decimal time for about a year between 1794 and 1795. Read more on Wikipedia.
The API powering this site can be explored starting here, or through the rendered OpenAPI description.
It is intentionally over-engineered to be used as an educational resource when teaching API design and REST principles.
The underlying script can be downloaded from PyPI or Github.