Claude knew the date and location of my daughter's bday party without me ever sharing that info

Maybe someone with more expertise can explain this: I use Claude as an ADHD coach and do daily check ins. Yesterday I asked for a to-do list and it mentioned the date and location of my daughter's birthday party. I asked it to tell me where it got the info from, since I'd never shared it, and I didn't receive an adequate explanation. Claude says it doesn't track activity in other apps so I'm stumped. I don't expect airtight privacy from these platforms, but this seemed particularly creepy.