Patrick Monahan of Train

Patrick Monahan of Train performs at KOST 103.5 Christmas Land at Microsoft Theater on Dec. 6, 2015 in Los Angeles.

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Train continues the tradition of holiday songs dashing to No. 1 on Billboard's Adult Contemporary radio airplay chart, as the band's version of "This Christmas" roars 8-1 (on the list dated Dec. 17; all charts will update Tuesday, Dec. 6, on Billboard.com).

"Christmas" becomes the 18th yuletide title to top AC. All have led since 2001, around the time that the number of new holiday releases increased and the majority of AC stations began making ratings-seeking switches to playing seasonal songs 24/7 for the first time in the format's history. (Since 2001, only the winter of 2009-10 did not produce a seasonal No. 1.)

"Christmas" was first released in 1970 by Donny Hathaway, who co-wrote the carol. (His original reached a high of No. 25 on Billboard's Holiday 100 chart in November 2014.) A year ago, Seal's version topped AC for one week; now, with Train's coronation, the composition becomes the first holiday title to top AC via different recordings. (Several artists in addition to Train and Seal have covered the classic, including Mary J. Blige, who took her interpretation to No. 2 on AC three years ago.)

Here's a holly, jolly recap of all the holiday songs to top the AC chart. Perhaps surprisingly, only slightly more than half (10) of the 18 seasonal leaders are covers of decades-old standards, including Train's; despite AC's reliance on familiarity, more modern fare by the likes of Mariah Carey, Kelly Clarkson and Josh Groban, among others, have also jingled all the way to No. 1.

Holiday No. 1s on Billboard's Adult Contemporary Chart (Title, Artist, Chart Date Reached No. 1, Weeks at No. 1)
"This Christmas," Train, Dec. 17, 2015, one (to date)
"This Christmas," Seal, Jan. 2, 2016, one
"Baby It's Cold Outside," Idina Menzel duet with Michael Buble, Dec. 20, 2014, three
"Underneath the Tree," Kelly Clarkson, Dec. 2, 2013, four
"Let It Snow, Let It Snow, Let It Snow," Rod Stewart, Dec. 8, 2012, five
"All I Want for Christmas Is You," Michael Buble, Dec. 10, 2011, five
"Oh Santa!," Mariah Carey, Dec. 18, 2010, four
"A Baby Changes Everything," Faith Hill, Dec. 20, 2008, three
"I'll Be Home for Christmas," Josh Groban, Dec. 22, 2007, three
"Frosty the Snowman," Kimberley Locke, Dec. 15, 2007, one
"It Came Upon a Midnight Clear," Daryl Hall John Oates, Dec. 30, 2006, two
"Jingle Bells," Kimberley Locke, Dec. 23, 2006, one
"Up on the Housetop," Kimberley Locke, Dec. 17, 2005, four
"Believe," Josh Groban, Dec. 11, 2004, five
"Sending You a Little Christmas," Jim Brickman with Kristy Starling, Jan. 3, 2004, one
"O Holy Night," Josh Groban, Dec. 28, 2002, two
"Simple Things," Jim Brickman featuring Rebecca Lynn Howard, Jan. 5, 2002, one
"The Christmas Shoes," NewSong, Jan. 6, 2001, one

With the inauguration of "Christmas," Train tallies its fourth AC No. 1. The group previously led with "Calling All Angels" (three weeks, 2004), "Hey, Soul Sister" (22 weeks, 2010-11) and "Drive By" (one week, 2012).

The new leader is from Train's 2015 holiday set Christmas in Tahoe (and is being promoted to the format fully for the first time this season). The band's new album, A Girl a Bottle a Boat, featuring the single "Play That Song" (which has reached No. 22 on AC), arrives Jan. 17.

Meanwhile, thanks to Train's takeover following Seal's, "Christmas" marks the first song (beyond holiday titles) in nearly 27 years to hit No. 1 on AC after a previous version led the list. On the Dec. 30, 1989, chart, Michael Bolton's "How Am I Supposed to Live Without You" spent its first of three weeks at No. 1. Laura Branigan's recording of the ballad had logged three weeks on top in 1983.