"I'm not sure 'hiding' it is the right--" Jim drags his free hand through his hair. "-- Term. It's complicated. You know that line about sufficiently advanced technology being indistinguishable from magic? Yeah that. Doesn't seem to hold true across other universes."

And then he groans. "Seriously? Okay. Shoes first. Come on." He begins the Arduous Process of dragging Chekov off to some nearby store. "And I meant event-wise. Last major one. Nero, the Gorn? Khan?"

That's maybe cheating a little bit. He knows Chekov's older than the last time Jim saw him. Which may or may not be his grand strategy for implying that he's also from a later point in the timeline.