We watched a blog by Sean Carroll: "Does Time exist? at https://m.youtube.com/watch?v=vWGuUr-6q9k.  Some philosophers hold that time is an illusion, but most admit its reality.  Classical physics holds that time is symmetrical, and it is only the law of increasing entropy that causes our experience of definite past, present and future.  How long is the 'moment" in time we experience?  Perhaps Planck time (10exp-44s)?. Classical physics and special and general relativity hold that time has singularities - a beginning and an end - though quantum theory holds that there is no singularity.