I had this problem with one of my Staffies, she would begin to bark at 3.00 pm every day to be taken for a walk.
I figured that she was hearing the bell ring in the local close by primary school to signal the end of the school day. However when visiting my father who lives out in the middle of nowhere, she still began barking at 3 on the dot.
What was more unnerving was that, even when the clocks changed for BST or GMT she still barked at three by the clock.
So either she could actually tell time by the clock, or was picking up on some unconscious reaction from me.
My current dog, a Shar-Pei, is also practically autistic and gets very angry if her precise routine is not adhered to, going off to sulk in corners and grumble to herself until things are back on schedule.