The addDays method returns a new DayPilot.Date value with the specified number of days added.
DayPilot.Date.addDays(days)days (int) - number of days to add.
The current value is not changed. The method returns a new DayPilot.Date object.
const start = new DayPilot.Date("2025-03-01T00:00:00");
const result = start.addDays(7);Days View [doc.daypilot.org]