Q:

What is considered a reasonable time under the Turner v. Driver case?

Turner v. Driver, No. 16-10312 (5th Cir. 2017), is a 2017 decision of the United States Court of Appeals for the Fifth Circuit that established a First Amendment right to record the police.
The court found that:

We conclude that First Amendment principles, controlling authority,
  and persuasive precedent demonstrate that a First Amendment right to
  record the police does exist, subject only to reasonable time, place,
  and manner restrictions.

Place and manner are much easier to define. But how do you consider a reasonable TIME in the previous citation? 

A:

"reasonable time, place and manner" is a phase that should be read as a term of art that has a meaning as a unit in First Amendment law. There is a body of First Amendment law that defines reasonable "time, place and manner" restrictions on First Amendment rights that is often not very specific about which part of the trilogy is being invoked.
An example, which would involve time (as well as other factors) under this test would be that it might not be reasonable to record a police activity using bright spotlights on the scene of an imminent police raid on building in a manner that destroyed the element of surprise for the police raid.

