In Chapter 1, George and Lennie arrive at a pool on the bank of the Salinas River. This is where they camp for the night. George makes it a point that Lennie remembers the area; Lennie is to return here if anything should go wrong at their next job.
Lennie--if you jus' happen to get in trouble like you always done before, I want you to come right here an' hide in the brush.
In Chapter 3, as dusk turns to night, George is in the bunkhouse and Lennie is in the barn with the puppy. Eventually, Lennie comes into the bunkhouse and gets into a fight with Curley.
In Chapter 4, on a Saturday night, when George goes out with the other ranchers, Lennie goes to Crooks' room and talks with him, Candy, and Curley's wife.
In Chapter 6, Lennie has retreated to the banks of the Salinas River. George and the other ranchers are on his tracks. It is around this time that afternoon is turning to evening.