Why did my YouTube watch time hours decrease in the Earn tab?

A drop in public watch hours is actually normal behavior, not a bug — the Earn tab tracks a strict rolling 365-day window, so hours earned exactly a year ago drop off as new hours get added today. If your recent viewership is running lower than the same period last year, your total will naturally decrease. It's also worth remembering that private, unlisted, and deleted videos never count toward this total, and Shorts views and ad-campaign traffic are excluded entirely. Add in the standard 48-72 hour validation lag, plus the periodic removal of flagged invalid traffic, and some fluctuation is expected. Steady, consistent uploads going forward are what keep new hours outpacing what's expiring from last year.