Calendar events missing from iPad

I sometimes need to find when events occurred (last time pets got required shots, most recent/past cancer treatment, etc). Search is failing to find any past events even though they are still shown on the calendar itself. It is also failing to find some future events, such as a monthly recurring meeting, one of which happened yesterday (not found by Search) and every month forever (Search found only one…in September 2026). This makes Calendar spectacularly unhelpful. I looked under Settings for a way to fix, checked Sync settings, followed some old instructions I found online, and also did a hard reboot. Search is still not finding anything past and only some in future. How can I fix this? I need iPad to act like an intelligent device and not require me to thoroughly and manually view every past calendar page seeking needed information. I am using iPadOS 18.0.1.