The totalMinutes() method returns the duration converted to minutes.
DayPilot.Duration.totalMinutes();
The duration converted to minutes. If the duration includes seconds or milliseconds the result will be a fractional number.
var minutes = new DayPilot.Duration("2020-01-01T00:00:00", "2020-01-05T12:30:15").totalMinutes(); // 6510.25