Photos: 99.7 [NOW!] Triple Ho Show feat. Carly Rae Jepsen, PSY, Austin Mahoney & More
Psy performs onstage during the 99.7 NOW Triple Ho Show in San Jose, California.

Taylor Swift broke a longstanding record on Country Songs, as did Lil Wayne on R&B/Hip-Hop Songs. Plus, new artists continued to break through.

Before we move on to 2013, here's a chronological look back at the biggest Billboard chart headlines of 2012.

Yesterday, we heralded highlights from January through June. Today, we pick up in the second half of the year, when, among other feats, Taylor Swift broke a longstanding record on Country Songs and Lil Wayne did the same on R&B/Hip-Hop Songs. Plus, new artists continued to break through, with acts like the Lumineers, Ellie Goulding and PSY galloping to the top of Billboard charts.

July 21
's "Party Rock Anthem," featuring Lauren Bennett and GoonRock, wraps its 68-week run on the Billboard Hot 100. The song departs as the longest-charting No. 1 hit in the chart's history, as well as the longest-lasting song by a duo or group. Among all acts, only Jason Mraz's No. 6-peaking "I'm Yours" (76 weeks) and LeAnn Rimes' No. 2 hit "How Do I Live" (69) has spent more time on the list.

Aug. 11
Katy Perry
matches Rihanna 's record for the most No. 1s in the 20-year history of Billboard's Pop Songs airplay chart, as "Wide Awake" rises 2-1. With the coronation, the two stars each boast nine No. 1s.

Aug. 18
Carly Rae Jepsen
's "Call Me Maybe" rings up its ninth and final week at No. 1 on the Hot 100. In addition to being named Billboard's Song of the Summer, it ties Percy Faith (and his Orchestra)'s nine-week 1960 No. 1 "The Theme from 'A Summer Place' " as the longest-leading title by a Canadian-born artist.

Aug. 18
The Lumineers
' debut hit "Ho Hey" logs its eighth and last week atop the adult alternative Triple A tally. As the stomp-and-clap folk song - now up to No. 3 on the Hot 100 - follows Gotye's "Somebody That I Used to Know, " Of Monsters and Men's "Little Talks" and Alabama Shakes' "Hold On" to the Triple A summit, the chart sported four consecutive No. 1s by acts making their first appearances for the first time in the list's 16-year archives.

Aug. 25
Ellie Goulding
ascends to the top of Pop Songs, as "Lights" lifts to No. 1 in its 23rd week. With its ascent, the song matches P!nk's "U + Ur Hand" (23 weeks, 2006-07) for the longest climb to the pinnacle by a woman in the chart's history. "Lights" goes on to become the top Pop Songs title of 2012.

Sept. 1
Taylor Swift
tallies her first Hot 100 No. 1 with "We Are Never Ever Getting Back Together." "#1 on Billboard's Hot 100!!?! This has been the most amazing week. (Jumping up and down)," Swift beamed via Twitter upon learning of her achievement.

Sept. 8
posts her record-extending 43rd No. 1 on Dance/Club Play Songs with "Turn Up the Radio." By the end of the year, Janet Jackson and Rihanna each rank second with 19 No. 1s.

Sept. 8
On his way to a seven-week peak at No. 2 on the Hot 100 with "Gangnam Style," Korean rapper PSY takes over as the main (mane?) man on the Social 50, spending his first of 10 weeks on top. His viral smash goes on to lead Rap Songs for eight weeks and Digital Songs for six.

Just in time for her debut at the judges' table on Fox's "The X Factor" (Sept. 12), Demi Lovato earns her first No. 1 on Pop Songs, as "Give Your Heart a Break" rises 3-1.

Sept. 22
Exactly 15 years and six months after the group's first visit to the chart, matchbox twenty notches its first Billboard 200 No. 1 with "North." The band's long absence surely helped its fans grow fonder of the group, which hadn't released an album of all-new material since 2002.

Oct. 6
Two weeks after matchbox twenty's long-awaited first Billboard 200 No. 1, P!nk likewise leads the list for the first time. After debuting on the chart more than 12 years earlier, she rules at last with "The Truth About Love." She had tallied five prior top 10s, rising as high as No. 2 with 2008's "Funhouse."

Oct. 13
Mumford & Sons
' "Babel" posts the biggest debut for an album this year, roaring in atop the Billboard 200 with 600,000 copies sold in its first week, according to Nielsen SoundScan. (It also becomes the folk/rock quartet's first No. 1 album). The set scores the best week for a rock title since AC/DC's "Black Ice" in 2008.

Nov. 10
Taylor Swift
's "Red" sells a whopping 1.208 million copies in its debut week, more than any album in a single frame since 2002, when Eminem's "The Eminem Show" opened with 1.322 million in its first full week."Red" easily debuts at No. 1 on the Billboard 200, securing Swift her third chart-topper.

Nov. 24
Maroon 5
spends its ninth and final week atop the Hot 100 with "One More Night." (Or, 63 nights at No. 1 ...) Not only does the reign extend the longest of the group's career, but it also ties the nine-week command of Carly Rae Jepsen's "Call Me Maybe" for the year's longest Hot 100 rule.

Dec. 1
's "Diamonds" shines brightest, at No. 1, on the Hot 100, marking her 12th leader on the list. With the coronation, she ties Madonna and the Supremes for the fourth-most No. 1s in the chart's history. Only the Beatles (20), Mariah Carey (18) and Michael Jackson (13) have sent more titles to the top of the Hot 100.

Dec. 8
The following week, Rihanna registers her first Billboard 200 No. 1, as "Unapologetic," her seventh studio album, launches at the apex. Not that Rihanna hadn't found love on the chart before: her first six sets reached the top 10 between 2005 and 2011. From matchbox twenty to P!nk to Rihanna, 2012 stands as a year in which multiple veteran acts added a first No. 1 album to their already impressive chart histories.

Dec. 8
Lil Wayne
breaks the record for the most entries in the history of Billboard's R&B/Hip-Hop Songs chart, as Nicki Minaj's "High School," on which he appears as a featured act, bows, becoming his 112th chart hit (dating to his first in 1999). Weezy - aided by rappers' modern-era practice of charting routinely as featured acts - passes the Godfather of Soul, James Brown, who banked 111 entries between 1956 and 1993. With Jay-Z next with 110 hits (as of this week), he and Lil Wayne, now up to 113 visits, seem likely to jockey for the mark going forward.

Dec. 8
One more Dec. 8 achievement: Rod Stewart dashes to No.1 on Adult Contemporary with "Let It Snow, Let It Snow, Let It Snow." The song becomes his first AC leader since "Have I Told You Lately" 19 years earlier (and his fourth AC No. 1 overall).

Dec. 15
Two months after Billboard revised the Country Songs chart methodology from core-country radio audience to a digital, streaming, and expanded radio hybrid (with similar changes enacted on the R&B/Hip-Hop, Rock and Latin Songs surveys), Taylor Swift's ninth week atop the ranking with "We Are Never Ever Getting Back Together" sets an all-time record for the most weeks at No. 1 by a solo female. The reign passes Country Music Hall of Famer Connie Smith's eight-week domination with "Once a Day" in 1964.

Dec. 22
Bruno Mars
lands his fourth Hot 100 No. 1, "Locked Out of Heaven," in a span of just two years, 10 months and one week, dating to the Feb. 13, 2010, arrival of his first chart entry, B.o.B's "Nothin' On You," on which he added vocals. That's the fastest collection of a male artist's first four No. 1s since Bobby Vinton rung up four over just two years and six months in 1962-64.

Dec. 22
Eighteen years after its release, Mariah Carey 's "All I Want for Christmas Is You" is a top 40 hit on the Hot 100 at last. The carol, from Carey's 1994 album "Merry Christmas," re-enters the chart at No. 29, a new peak position (and rises to No. 25 this week). "Christmas" didn't reach the Hot 100 upon its original release, as it was not then available as a commercial single; per rules at the time, such tracks were not eligible for the chart. The song did, however, rise to No. 12 on the Radio Songs survey the week of Jan. 7, 1995, marking the highest rank for a holiday song in the chart's 22-year history.