Neil Sedaka's entire career was one long subtle assault on Christian civilization, and this is one of the most ominous and threatening songs he ever recorded. Let's examine it.
First, the structure. Donne-ishly (I believe the irony to be deliberate, a planned desecration), there is a unifying conceit: The "girl" is associated in turn with each of the twelve months of the year, which are referred to by their pagan Roman names. A further elaboration on this is the evocation of the "pinup calendar", an example of modern American paganism in which photographs (graven images) of prostitutes are displayed in a sort of disposable shrine.
Naturally, the first month is January, named for Janus, the two-faced Roman "god" of deception, hypocrisy, and so on: The alert listener is given notice from the start of the first verse that all is not as "innocent" as it seems. The next two lines are devoted to lulling the listener: February is quite innocent (except, of course, for the pagan name), and March -- "I'm gonna march you down the aisle" -- is a crumb thrown to decent chastity and womanly submissiveness.
Then all Hell breaks loose: The Easter Bunny is a pagan fertility symbol, just as the conventional secular celebration of Easter is a re-enactment of pagan fertility rites. The "girl" has suddenly and with very little warning become a "fertility goddess", "smiling" at her "worshipper". Do your children need to be exposed to this?
In the second verse, Sedaka again lulls us for a bit, drawing another image of appropriate womanly submissiveness: He asks her father's permission to take her to a dance. Of course, we all know what is symbolized by dancing, and I assume we've all heard the phrase "off like a prom dress". The innocence is skin-deep at best, and the "prom" happens -- by chance? -- to coincide with the pagan festival of the summer solstice. The remainder of the verse ventures into increasingly sexualized images of fire, heat, and immodesty. There is also a veiled reference to the Apocalyptic nuclear conflict novel On the Beach, by the infamous pagan Nevil Shute. You may draw your own conclusions about what it means when an "innocent" popular song sexualizes the death of the planet earth and the human race.
In the final verse, Sedaka pulls out all the stops. The gloves are off, and we see a rapid burst of primitive, pagan, and diabolical imagery: The "virgin" is illuminated by "torches" at her deflowering; the unchaste young lovers Romeo and Juliet, with their blasphemous act of suicide, are associated with the Satanic festival of Halloween (Samhain). In November he "gives thanks" for at this point what can only be considered carnal relations of an exceedingly dubious variety.
We finish up with the Babylonian symbol of the Christmas Tree or "Everything Tree", used to signify the incestous bloodline of Nimrod and his mother. The "girl" appears underneath this abomination: She is an offering, a sacrifice.
In closing, let's consider again the "pinup calendar" image. Is there even more to it than we've already seen? I don't like to run off chasing faint hints or arbitrary correlations, but I think I'm on safe ground in claiming that there is indeed more here. The calendar is time. Time is ticking. The prostitute, the "liberated woman" of feminist myth sits and watches as the observer descends further and further into paganism. The apparent chastity in the early verses is not just misdirection: We are meant to be exposed here to a progression, a long slide down the slope of subjugation to an unnatural female power structure. What we are seeing here is an allegory of Christian man led down the primrose path to Goddess-worship. The feminist on the wall "smiles" down at her "recruit", who ultimately sells his honor and self-respect to gain the cheap "sacrifice" waiting beneath the Tree of Babylon.
It's a chilling image, is it not?
I love, I love, I love my calendar girl
Yeah, sweet calendar girl
I love, I love, I love my calendar girl
Each and every day of the year
(January) You start the year off fine
(February) You're my little valentine
(March) I'm gonna march you down the aisle
(April) You're the Easter Bunny when you smile.
Yeah, yeah, my heart's in a whirl
I love, I love, I love my little calendar girl
Every day (every day), every day (every day) of the year
(Every day of the year)
(May) Maybe if I ask your dad and mom
(June) They'll let me take you to the Junior Prom
(July) Like a firecracker all aglow
(August) When you're on the beach you steal the show.
Yeah, yeah, my heart's in a whirl
I love, I love, I love my little calendar girl
Every day (every day), every day (every day) of the year
(Every day of the year)
(September) Light the candles at your Sweet Sixteen
(October) Romeo and Juliet on Halloween
(November) I'll give thanks that you belong to me
(December) You're the present 'neath my Christmas tree.
Yeah, yeah, my heart's in a whirl
I love, I love, I love my little calendar girl
Every day (every day), every day (every day) of the year.
Lyric by Neil Sedaka/H. Greenfield