Other than the instance you mentioned, the only time months are mentioned is in VDT. A sailor suggests wintering on Ramandu's Island and returning home in March or April. I think he's the Galmian sailor, but I'm not quite sure. I've never seen or heard of a complete Narnia calendar, and I really doubt there is one; C.S.Lewis wasn't detailed enough for that.
Sorry, that probably wasn't much help.

No, that is of help. Finding out for sure that there isn't a calendar is just as important. If there is not one, then I can take the liberties and create one...but if there was one, I wouldn't want to do that! So, thanks!

I have to agree with daughter of the king. Since Narnia did begin with a king and a Queen of Earth they probably brought on the same seasons and months of their world to the world of Narnia and there is that passage in VDT at Ramandu's Island where I'm assuming Rhince spoke about the months like how earth people would. The Telmarines are from earth as well and I'm sure they carried on tradition on how human beings would.

Also, in SC, the queen and Rilian go maying. I don't think there's a direct reference to the month, but since maying is done on May Day, and May Day is a celebration of the first day of May, it could be at least assumed that there is a Narnian month of May.
I believe Greenroof corresponds the month of June or July. I think I read that in Paul Ford's Companion to Narnia, but I don't remember...

Great find ChristProclaimer. You explained that well enough to where that's probably what it is and I believe it 100 perecent now. Totally makes sense

Thanks, guys!

It is possible that there are nicknames for months, or the months were renamed, or there are more months in Narnian years (which I doubt for some reason). But there are month names mentioned in Narnia.