Scents trigger memories and feelings. It's weird.
I smell of rubbing alcohol and Warning! Needles! pops in my head. I sniff the old bottle of the floral room spray I used in college and I'm suddenly a freshman in 1987 (Will I like college? Will I make friends?)
Then there's the chlorinated pool.
I smelled my first one at swimming lessons when I was little. I was terrified. The pool was huge. And deep! I didn't trust the teachers. Who were they? How could they teach me to swim? What if my head went underwater and nobody pulled me up? I just knew I was in danger.
The smell of chlorine still triggers my Be nervous! reaction. Of course, more evolved parts of my brain follow up with Whoops, we don't seem to be at swimming lessons. No need to be nervous. Calamity closed..
That's my reaction to the scent in the daytime.
Years ago, on the way to a pool after sunset, I caught my first burst of chlorine and noticed it didn't hit the be nervous! nerve. Instead it was relaxing and nostalgic- like when you first smell the beach (or the hotel air freshener) on a trip. A complete opposite reaction.
I think I know what's going on.
My swimming lessons took place in bright daylight. Any after dark swimming was done on special occasions, either with friends or at a hotel pool on vacation.
Somehow, my brain does this math.
Chlorine scent + Daylight = Danger!
Chlorine scent + Night = Ah, it's great to be on vacation!
Brains work in weird ways.