A depressive slump, or just an anniversary?

I was feeling unusually down the past five weeks and couldn't account for it. Slept poorly, stopped exercising, etc. And blamed myself for feeling badly because I'd fallen off my wellness routine, which is usually very effective at keeping me stable.

Even discussing it was frustrating, because my support people asked if anything had happened to cause it, and I couldn't find an explanation that felt right.

This morning, I was journaling and it hit me all at once. I went tearing through my old diaries, and yup, there it was. It's been four years since my inpatient hospitalization and starting meds.

It's so strange to me that anniversaries like these have an effect on me when I'm not even aware of the date or its significance. I had a similar unexplained experience of low mood once and checked the diaries...it was the exact day and month an important romantic relationship had broken up, years before.

Today, I'm feeling back at baseline. Simply having an explanation that lands properly in my heart and gut cheered me up immediately. Before I knew what was going on, I felt confused, self critical, and was getting anxious that this low period might mean a depressive episode. But I don't feel that way anymore.

Has anyone else had weird experiences like this with anniversaries you weren't even consciously aware of? Curious to hear the experience of others.