Do Bears know time?

In late January 1973 I had begun a new life in the beauty of Alaska.
Our base mainly operated in the winter which was testing time so in the summer we had a lot of down time. I was an explorer and was going to see as much of this land as I could. I needed this place to wash me clean of the memories.
Make me feel young again.
Summer days up there worked this way. We would have daylight for twenty or so hours with only 4 hours of twilight. The winter was the reverse. 4 hours of evening followed by twenty hours of dark and much colder but there was a side benefit.....no mosquitos.
I became an avid fly fisherman learning the art.
Our favorite place was Paxson Lake. There we would fish in the numerous streams for the Arctic Grayling a fish similar to the salmon and very tasty.
We practiced catch and release just enjoying the outdoors and fishing.
I remember we were about fishing when one asked what time is it. Another answered 3 o'clock. AM or PM?? Hell we did not even know. We would fish till we got tired and hungry. Keep a fish, fry and eat. No waste no want. No track of time.
One late summer day I went by my self to go fishing.
I went over to a stream I liked and got started. We were now having a more normal type day. The evenings were chilly. Winter was coming. The snow line ever moving down the face of Mt. McKinley. Things were going along fine when I heard the noise up stream. Lots of splashing and grunting. I was downwind when I smelled it.
A bear.
They have a stench that once you smell it you never forget it. It is like primeval in your memory maybe reflecting back to the time when man rose taking on the cave bears for survival.
It was coming my way.
I quietly exited the stream to move off. What a bear wants a bear gets. No arguments with 900 pounds of muscle and a really bad temper to boot.
I found my self trapped. In my wander I failed to notice the bank. The area was flat up to where a dirt cliff rose about 8 feet. Too steep to climb up. To far either way to get around.
I heard the loud snort to my back. I turned very slowly to see about 25 yards from me this huge gray silver back grizzly. I could hear him sniffing and snuffing the air with that huge nose. He knew something was there but was unsure at first. Bears have terrible eyesight but their sense of smell is incredible. He stood up towering to 8 foot easy. The front paws and claws were bigger than my head. He let out the loud noise, a bear roar to let me know he knew I was there and he wanted to know my intentions. I could see he was old as his marks and scars were visible.
I slowly removed my pistol from the holster. It was little help. A Ruger 357 mag Security Six revolver. I had six 157 grain semi jacket soft points. Little effective on this monster in front of me. More for wolves or humans. I figured this much out. I had six, five for the bear, and one for me. You don't usually survive a bear mauling. I had seen the damage they could inflict.
We stood across from each other only separated by 25 yards.
I could feel my heart pounding in my chest as I stared like our human ancestors had probably stared at this massive, smelly, beast in front of me. I held no ill will to him.
The bear made some grunting sounds. Strange noises. He suddenly lowered himself to all fours. Pissed on the ground, I caught his meaning if he meant one.
The grizzly went back down the stream crashing and banging about.
I had to force my knees to unlock so I could sit down before I fell down.
The adrenalin rushing giving me the familiar shakes. This time from a different battle.
A more primeval battle.
I was again a survivor.
Silly me, I had forgotten to bring clean underwear.
Commando time.
Back to fishing. AM or PM?