  Time crystalline structures are characterized by regularity that
single-particle or many-body systems manifest in the time domain, closely
resembling the spatial regularity of ordinary space crystals. Here we show that
time and space crystalline structures can be combined together and even
six-dimensional time-space lattices can be realized. As an example, we
demonstrate that such time-space crystalline structures can reveal the
six-dimensional quantum Hall effect quantified by the third Chern number.
