Time: Near Future (positive)

Fifty years from now, technology will likely have escalated exponentially thanks to current advances in quantum computing and fiber optic data transfer. Quantum computing will necessitate the change of the basic binary (0's & 1's) computing language to be upgraded to a quaternary one (0,1, 2 & 3), meaning an exponential explosion in the amount of data that can be processed. Fiber optic cable can support multiple frequencies on the same line, delivering internet AT THE SPEED OF LIGHT! I can only hope virtual reality sensory feedback systems can keep up. I am a SAO fan!

Time: Present(Recent past)

Present implies something recognizable today +/- 50 years. Fifty years ago we were still four years away from landing on the Moon, computers were still in their infancy, black Americans gain the right to vote, and St. Louis Arch is completed in Missouri.

In the fifty years before that, steam power was giving rise to internal combustion, The Wright Bros became  the inventors of powered flight, and television broadcasting brought news instantly to all.

Time: Past

Time is another important aspect. Knowing when your story takes place can help shape many aspects of a culture. Especially what technologies may or may not be available.

In a recent past setting, post dark ages- pre automobile, the divide in the worlds first and third world cultures was as stark as the tribal Masai warriors of Africa and Victorian England. Ancient past might be include Egyptian Pharaohs, crusaders of the holy roman empire, or maybe feudal Japan.