The datePattern property (string) specifies the pattern used to format a DayPilot.Date value as a date without the time part.
DayPilot.Locale.datePattern'M/d/yyyy'This format string uses the pattern syntax supported by DayPilot.Date.toString().
const locale = new DayPilot.Locale("en-custom", {
datePattern: "dd.MM.yyyy",
// ...
});
DayPilot.Locale.register(locale);Header Date Format [doc.daypilot.org]