The first thing a player sees in The Legend of Zelda: Majora's Mask is a group of carpenters beginning construction on a platform. Three days later, the player must return to that same location where they discover that the carpenter's platform has tripled in size. The player then travels back in time to the first day where they witness the construction beginning anew. It's no accident that players begin and end their first of many three day cycles next to the ever-growing platform, it teaches players that time has a real, tangible effect on the world of Majora's Mask. This effect is made possible by the game's unique, three day mechanic which unifies the narrative and gameplay of Majora's Mask to bring meaning to the player's actions and life to the world they inhabit.
Sid Meier famously stated games are a series of interesting decisions...involving some kind of trade off. Many side-quest rich games provide decisions in the form of long checklists and give players the freedom to tick them off in any order they wish, but often fail to furnish any meaningful trade off. In Skyrim or The Witcher 3, it rarely matters if you chose sidequest 'A' or 'B' first because the other will wait patiently for your return. In these situations, the narrative and the player's freedom work against each other: NPC warn the player to act fast, for the fate of the world rests on their shoulders, but there are no game mechanics that give any weight to their urgency. Players are free to leisurely meander from side-quest to side-quest and the juxtaposition can break a player's sense of immersion. Yes, having lots of options is good, but having lots of impactful decisions is better. The three day cycle in Majora's Mask allows that. Not only does pursuing sidequest 'A' mean you won't have time for sidequest 'B', but if you're not fast enough you might not have time for either. When the world is ending in three days, urgency becomes organic and the importance of your choices are self-evident.
The three day cycle not only makes decisions more meaningful, it actively pulls the player further into the narrative. Because the world resets every 72 hours, NPCs are allowed three days of unique scripted actions, which is far more immersive than the repetitive holding patterns found in most open-world games. The default scripts in Majora's Mask are bleak in tone, but player intervention can result in a happier timelines. Importantly, it's not possible to help every NPC in every cycle, so players will eventually witness multiple timelines for various NPCs and see firsthand how big of a difference their actions made. Everytime the player chooses to help one NPC over another, they are reminded that the only way to truly save everyone is to push forward with their quest, defeat the final boss, and break the apocalyptic three day cycle.
Majora's Mask's three day cycle certainly has drawbacks: it can get repetitive, players have to wait for events, and losing progress every 72 hours can be frustrating, but overall it's a unique mechanic and it solved a lot of problems for Majora's Mask that still plague action-adventure games today. The time limit adds true urgency and meaning to the players' decisions and enforces the illusion that this is a real intricate living world for the players to inhabit and explore.