Can time be quantised? Would it be the smallest distance between two photons moving in the same direction or the shortest wavelength?
"Can" time be quantized? Yes it can. We have atomic clocks working for us after all, giving us increments of time.
Is this phenomenon sufficient to say time in general comes in increments? No.
The same is true about quantization of space. Space can be quantized. A crystal is a clear manifestation of quantization of space. This is not sufficient to conclude that space is quantized.
This question morphs into digital physics, which has problems with the symmetries and localities of quantum mechanics and quantum field theories that have been validated by a large number of experiments.