However, others blamed it on a long-distance relationship ultimately causing their break-up.
Rumours say the 10 year age gap became a big issue for the couple when they dated for two months back in 2010.
Popstar Ellie Goulding said she originally set Calvin and Taylor up when she introduced them at the BRIT Awards after-party in London in 2015.
Tay even thanked him at the i Heart Music awards calling him "the most amazing person".
Splitting up that September, Taylor's team said their whirlwind romance ended as Tom wanted too much publicity from the relationship.
Ending the relationship for good, the music video sees Taylor wearing a number of things that give the hint the song is about Jake – including a diamond bracelet he apparently gave her for her birthday, and a scarf that she was seen wearing on one of their dates.
Taylor was just 19 when she sparked a romance with a then 31-year-old.
This Is The Moment I Knew is said to be about Jake.
Apparently he stood her up at her 21st birthday party and she spent the evening crying in her bathroom.