nah, training data is not why it answered this (otherwise it would have training data from many different years, way more than of 2025)

It also happened last year if you asked if 2026 was next year, and that was at the end of last year, not beginning

This instance actually seems more like 'context rot', I suspect google is just shoving everything into the context window cuz their engineering team likes to brag about 10m tokens windows, but the reality is that its preeeeettty bad when you throw too much stuff.

I would expect even very small (4b params or less) models would get this question correct

This is actually the reason why it will never actually become general AI. Because they're not training it with logic they're training it with gobbledy goop from the internet.