Is there an equivalent of the Planck length for time? Is there an equivalent of the Planck length for time? I'd just like a term I may use (high-level) for a similar "unit of time"?  I am not looking for a debate on how discrete time might be, but if there is a term I can use that complements Planck's constant for space, I'd like that.
This doesn't help at all.
 A: Planck time - the amount of time it would take a photon (or other particle travelling at the speed of light) to cross a planck length - the fastest known speed travelling over the shortest known distance. Time, as distance divided by speed, doesn't get much smaller than that.
It is about 5.39 x 10-44 seconds
Which can be expressed as 0.0000000000000000000000000000000000000000000539 seconds
Or rounded to one ten million billion billion billion billionths of a second
A: There is a smallest measurable time interval, known as Planck time, which is the time required for light to travel the smallest measurable length which is known as the Planck length, $$\ell_\mathrm{P} =\sqrt\frac{\hbar G}{c^3} \approx 1.616\;199 (97) \times 10^{-35}\ \mathrm{m} $$. 
So, the Planck time will be $ t_\mathrm{P} = {\frac{\ell_\mathrm{P}}{c}}\approx 5.39106 (32) \times 10^{-44}\ \mathrm{s} $.
If two points are separated by a length less than the Planck length, we would be unable to tell the difference between those two points. Spacetime geometry itself might not be meaningful below the Planck length (we don't know yet what happens below the Planck length).
The Planck length limit comes from the assumption that neither quantum mechanics or relativity fails. So we don't know what happens below that length as the physics is not quite up to the handling at that scale. 
