Lot of you fellow caps are asking a lot of similar questions (great minds think alike) so allow me to write a short FAQ list.
1)Yes earth signs are compatible, but be prepared for stubborn battles unless you and your love have similar interests and direction
2) fire signs like Sagittarius are attractive because of their philosophical nature but will tread on capricorns nerve rather quickly once you realize those deep philosophical conversations don’t have any follow through or practical applications.
3) there is no exact cut off date, the dates given are simply a a date for simplicity, the closer you are to that date the more traits of the previous/next sign you will display/take on. Think of each sign having three stages. Capricorns who show signs of Sagittarius, capricorns, and capricorns who show signs of Aquarius.
4) you are not just your sun sign. You also have a sign for each planet which effect how you act.