The Firework singer, a vocal Clinton campaigner, documented her trip to the polling station with a series of Instagram stories and told her fans as she was riding in a car on the way there that she was filling in her ballot said "cos it's my birthday and it's the greatest gift I could give myself."

Katy also shared footage from the polling station, which had reportedly closed as only staff were present, and she yelled from behind the camera, "I'm here and I'm ready to vote!! I'm voting!!" as people could be heard cheering in the background.

The 32-year-old, who wore a stars and stripes coat and matching bag, also shared a video of herself placing her voting slip into the box and she told viewers, "Happy birthday to me and happy birthday to you HRC."

"GAVE MYSELF THE BEST BIRTHDAY PRESENT EVER BY VOTING TODAY" she wrote in the caption. "Wish @hillaryclinton a Happy Birthday tomorrow with your EARLY vote."

Katy also documented the rest of her birthday on social media. Before her vote, she was presented with 'bacon cake' with candles on and given presents. Later that evening she went to Kanye West's concert at The Forum in Inglewood, California and she notably filmed herself in the audience as Kanye sung his stinging lyric about Taylor Swift, who is thought to have a rivalry with the Roar singer. After the show, her friends gathered to present her with a birthday cake and sing happy birthday.

Clinton, who turns 69 on Wednesday (26Oct16), also caught a concert to celebrate her birthday. She watched Adele perform in Miami, Florida and the British singer urged her audience to vote for Clinton over her rival Donald Trump.

“Don’t vote for him, that’s what I’m sayin," she said. "I can't vote but I am 100 per cent for Hillary Clinton. I love her."

The U.S. election takes place on 08 November (16) but Katy isn't the only one casting an early vote. Justin Timberlake flew to his home state of Tennessee to hit the polls this week (beg24Oct16). He snapped a selfie at the polling station and it was reported he could get into trouble for it, but local District Attorney Amy Weirich said they would not be investigating the issue.