The DayPilot.Calendar.columns.find() method returns the column with the specified date (and id).
DayPilot.Calendar.columns.find(stard[, id]);id (string | number) - id of the resource (optional, only applies to the resource calendar mode)
start (string) - start date of the column in ISO format ("2025-01-31T00:00:00")
DayPilot.Column object if the column is found, otherwise null