I learned this from Jeff Warner, probably 20 years ago, on hearing him sing it at a concert, scrawling the words on a piece of brown paper bag and talking with him about the song after the concert.
The scrap of paper is long gone, but I've been singing it ever since. I'm very happy to learn the tune's origin, and will be sure to credit Paul Bellamy whenever possible.

Here's how I sing it. I do say "It's almost day". I absolutely see the logic of the original words, but I'm afraid I must have changed them unintentionally very early on in my singing of the song, and by now it has a life of its own in that version. I know a number of folks who learned it from me. There are a couple of other changes that have crept in, who knows how.

As silver moonbeams round me shine,
I swear with Reason as my teacher
That if my midnight glass runs right
I will boldly call for another pitcher

Ch: It's almost day, it's almost day,
    Why should we forsake good liquor?
    Until the sunbeams round us play
    We will joke and pass around the pitcher.

They say that we must rise each day
And go to work to rise much richer.
But what is that to you I say
Compared with mirth, my friends, and pitcher.

How well I love a handsome lad,
No snivelling milk-sop Jimmy Twitcher
Who loves a lass, and loves a glass,
And boldly calls for another pitcher.

A man may boast a handsome wife,
And yet strange presence may bewitch her.
Unyoked I'll lead a single life,
And boldly call for another pitcher.

Cheers,
John