what the season changes
Halloween runs on the real calendar, from October 10 to the end of the month, read off your system clock rather than anything in the world. While it is on, most enemies have a small chance to drop a Goodie Bag, a lot of them wear costumes that change nothing but their sprite, a few seasonal enemies join the spawn pool, and pumpkins start growing by themselves on grass. Hearts and mana stars are swapped for Candy Apples and Soul Cakes, which work exactly the same and are purely a reskin.
The season also opens Halloween-only stock at several NPCs and bolts seasonal drops onto ordinary enemies. That makes October the only window for a long list of vanity, the themed hooks and pets, and costume pieces that have no recipe. Goodie Bags come off almost anything, they stack, and their contents are the bulk of that list, so passive farming through the season does most of the work.
the weapons with a hidden rule
The Bladed Glove and the Bloody Machete only drop from weak enemies, and the game has an exact definition of weak that nothing on screen tells you. An enemy qualifies if it drops at least one copper while dealing under 40 damage, carrying under 20 defense and dropping under 5 silver. Those thresholds scale with world difficulty, so the pool of qualifying enemies is different in Classic, Expert and Master rather than fixed.
Two things deliberately do not move them: the Journey Mode enemy difficulty slider and the extra stats For the Worthy and Zenith worlds hand out. Cranking the slider to make a farm spicier does not disqualify the enemies you were farming, which is useful, because the practical approach is a low tier surface farm rather than anything dangerous. Zombies and other early night spawns are the target here, not whatever is currently killing you.
pumpkins
Wild Pumpkins appearing on grass is the quiet reason to log in during October. Out of season you grow them from seeds a plot at a time, which is slow. In season, one walk along a long stretch of surface grass can cover an entire Pumpkin Moon Medallion with room to spare. Add Ectoplasm from a Hardmode dungeon and a few Hallowed Bars and the medallion stops being a project you keep postponing.
turning halloween on out of season
There are two routes inside the game. Push the Pumpkin Moon to wave 15 before dawn and the season switches on for the whole of the next in-game day, no matter what the real date is. That closes a neat loop: the medallion farms the pumpkins for the next medallion. The other route is world creation, since a world made on the secret seed hocus pocus keeps Halloween running permanently.
Outside the game, setting your device clock to any date in the window works. Third-party launchers can fake a date for a single program if you would rather not move the whole machine, and on console you disconnect from the network first and set the clock by hand. One thing to watch: a world created with a blank seed during the real Halloween window quietly picks up the pumpkin season flag and keeps it forever.

