Is it "tomorrow" after midnight? Or is it still "today"?

Let me start with an observation: Let's say it's half past 12 and you're heading off to bed, I personally would say

Tomorrow I have to get up early for work

And as far as I know all my friends would too, but when I got into a discussion with a friend about this we looked up the definitions where tomorrow is

the day after today.

and today is

on or in the course of this present day.

and day is

a period of twenty-four hours as a unit of time, reckoned from one midnight to the next, corresponding to a rotation of the earth on its axis.

(all quotes taken from the google.com dictionary)

Although there are a couple of more options for day both on the google dictionary and a couple of other dictionaries I checked, none define the term in regards to sleep cycles. So, is this usage actually uncommon in English? Or is this simply a fault in the dictionaries I checked? Or am I misinterpreting the definitions?

And just to be clear, I would have expected tomorrow to be defined as something along the lines of

Tomorrow. The time after one wakes up, or — if one is not sleeping — after the time the majority of people are asleep (normally around 4–5 AM).

But as I am not an English native speaker I did want to check whether that usage really isn't correct in English speaking countries.

Solution 1:

Whatever time it is, it's always after midnight. As in, after some midnight that went before.

Seriously, this is a choice of being figurative or literal. Whenever people correct this they do it teasingly. We all know what is meant. We're having fun with the fact that our expectations fail us when in an unfamiliar situation.

A student going home at the end of a school year might say to a class mate, "See you next year".

A student going home for christmas break and not returning until January might also say, "See you next year". This is literally true but is just being silly.

So if you say,

Tomorrow I have to get up early for work

after midnight I would only correct you to have a bit of fun with you.

What's being conflated here is that tomorrow means the next day, but it also usually means after we go to sleep. The usual expectation breaks down when you stay up after midnight.

Actually this happens to me most often when I say, "I'll do that tomorrow" and it happens to be Friday. Since I don't work weekends people know I mean Monday. But they tease me anyway.

The literal definitions of our words are the anchors that keeps them from drifting onto the rocks of the incomprehensible, but despite that, we do give them a long chain.