I have had this same issue myself after traumatic things happen.  I went through a bad break up one year in the week leading up to Thanksgiving, and for quite a few years afterward I would find myself getting nervous and anxious right around mid-November.  It did fade.  A friend of mine gets tense, moody and emotional every year as the anniversary of her mother's sudden death approaches.  I think it's actually on the spectrum of Post Traumatic Stress Disorder.  We tend to think of that as afflicting people who have served in combat or something similar, but I think there's differing degrees of it and what you are describing definitely sounds like that could be the case.   I was diagnosed with PTSD after watching my son go code blue in the ER (he was septic) and watching the doctors try to revive him.  For a minute, I saw them lift up his little body and he was blue and limp, and I thought he was dead. Thankfully he recovered, but even months later, I could be doing something as innocuous as just driving down the street and that image would randomly flash through my mind.  No triggers that I could identify, but it got to be debilitating because it would then trigger a panic attack.  I finally saw a doctor about it and started taking Lexapro, but I think the passing of time helps a lot, too.  Your body has been conditioned to go into fight or flight response around the same time each evening.  It will eventually unlearn that response, but it might take a little while.  Being aware of it will be helpful for you...hope it gets better soon.

That sounds like a great idea.  Your friend will provide distraction and you're right, being in a different environment might break that association your brain/subconscious has with the nine o'clock hour.  I hope it works for you!