public class TimeInterval
This class describes the start and end times of an image exposure. For a
single image it is assumed that that the timestamp recorded by the camera
is at the end of the exposure so the start can be found by subtracting the
exposure time. A similar principle applies to a sequence of images that has
been combined by GRIP into one image. Times are represented internally as
ms since 1970.0 UT, in the usual Java way, so time zones are irrelevant.