date-to-jdn Converting Gregorian calendar date to Julian Day Number (JDN). Install npm install date-to-jdn Usage import dateToJdn from "date-to-jdn"; dateToJdn(new Date('2024-02-09')); //=> 2460370 // = 2024-02-29 12:00:00 UTC API dateToJdn(date) date Type: object A Date object.