Routine ??!?!??!?

My colleague: why do you drink coffee at 4pm? How are you going to sleep after this?
Me: it's a fourth one and not the last one 🙂

I literally don't understand problem of drinking coffee at 4pm, I never knew it matters for someone. Like, I can have a coffee at 11pm and have a great eep (if I'll let myself sleep before 4am)