Ideas:

Glyphs ought to be 'read' according to the context. Here we have the two sharks, perhaps symbolizing shadows. Then it would seem natural not to 'read' the rectangles as periods of time but rather as the areas of space which are shadowed.

Although equally reasonable is to always 'read' this type of glyph as an area of time-space; time and space not being possible to imagine one without the other.