That is, to the original NES game from 1987. after the original was a huge hit, the sequel "Zelda II: The Adventure of Link" was released shortly after.
Since then, every Legend of Zelda game has been a prequel to the original NES game! The Super NES game A Link to the Past was a prequel to the NES game, and the critically acclaimed Ocarina of Time was a prequel to the SNES game.
The actual timeline of the Legend of Zelda is a heated internet debate and where each game is placed in the timeline is nearly impossible to determine. It is said that there is a secret Nintendo document that shows how each game fits in an overarching story, but they have chosen not to release it because they don't want to lose flexibility for future games.
If you have a few hours to spare, just google "Zelda Timeline" and see for yourself. This goes to a graphic showing one of the least controversial timelines around.