"Triptych" implies a work of several related panels, arranged horizontally and sequentially. However, it can also consist as a sequence of one, or several, images within one another.
Time is said to proceed in a linear, step by step, process. Since it is the mind that processes time, mind and memory can also view time as images imbedded, or emerging, in or out of one another, proceeding not only linearly, but also in depths. The triptych (or multiptych) then becomes not a linear but a view into the depth of time and space.
Often, these "integrated" images may reflect different "time frames", from different periods - like memories out of the past.