Tomorrow will bring no mail, because Monday is when Christmas is “observed.”

A peculiar word; it’s as if we experience it on 25th, but the next day we stand back and watch it.

Of course there will be no Christmas to observe tomorrow, only its aftermath. The tree’s lower bowers will be empty, all the packages opened. If there’s a Santa statue around, he’ll look like he missed the bus.

No one will want to hear Christmas music, which reminds you how those melodies are remarkably date-specific. On the 24th, you hear something from “A Charlie Brown Christmas” soundtrack, and you’re stopped in your tracks. You’re a kid again, but with an adult’s bittersweet perspective. It hits you hard.

It’s that gentle piano-driven small-combo sound that captured the quiet joy of the season, you know? It somehow made a 10-year-old wistful for the memory of being 9.

I almost avoid it every year because it just lays me low. But that’s the beauty of these days, the way they bind the filaments of memory into something that slides through our hands like a silken rope, played out over the years with ever faster speed.

If you hear that song tomorrow, your heart is stone. Sorry, Linus. Christmas is “observed” on Monday in the same way you see an eclipse on an overcast night.

However, because the Postal Service observes it, no mail will be delivered. So you’ll have to wait until Tuesday to get back the cards you sent out with bum addresses. With the RETURN TO SENDER stamp, the one with the old-timey hand with the pointing finger that always makes you hum a little Elvis.

If you’re lucky, you’ll get some cards from people who missed the deadline.

I know it’s proper to get your cards out ahead of time, so people can sit by the tree and pass them around and drink mulled wine and say, “Look how the children have grown. … Who are these people again?”

Ah, tradition.

But there’s something about cards arriving after Christmas that’s nice.

First of all, it says you’re not the only one who was stressed about the cards this year.

I was, too. The printer broke, because printers are designed to turn into bricks the moment they hear the words “Did you print off those labels like I asked you last week?”

It’s those last six words that fuse every circuit. Turns out one of the ink tanks was low, and you can’t have that. The Post Office sends it back with a stamp that reads: UNDELIVERABLE; NO MAGENTA.

All our cards got out in time. But some of the envelopes were upside down in the box. That means that during our assembly-line procedure for sending out our fondest personal greetings, the labels were incorrectly affixed.

“Oh, no!” I told my wife. “We’ll be judged harshly, mocked with brackish laughter and struck from their Christmas card lists.”

And then I put on the “A Charlie Brown Christmas” music to make everything right. It’s a precious remnant of the season. Today’s the last day we’ll want to hear it.

Tomorrow if the malls opened their doors and blared “The Star-Spangled Banner,” I think we’d all be fine with that.