You can always change the year in FreePlay. That's part of what makes it Free Play. In fact, if you make Almeida American then the player must change the year because by default it starts in 1682, America doesn't exist, and the player will never see Almeida. The 'model.date' lines in the definition for the "Almeida" model in "initModels.c" mean that if the player chooses that character, the date will be set to June 1812, but there's nothing to prevent the player from changing it again after choosing the character.
If you want to lock the time, one option is to make it a full storyline rather than a sidequest, which has the added benefit that it then appears in the storyline selection list so more people will find it. Another would be to only allow the sidequest to trigger if the year is at least 1812. (You can't check for the year being exactly 1812 because by the time the player reaches level 10, it might be 1813 or later.)
Otherwise we'll need to figure out a way to lock the date for models with an active 'model.storytitle' line in their definitions. José Joaquím Almeida isn't the only FreePlay character who will look odd if the player changes the year after selecting the character - imagine playing Francis Drake in the "Golden Age of Piracy" period, doing the "Angelique Moulin" sidequest, and digging up his own sword.
If you want to lock the time, one option is to make it a full storyline rather than a sidequest, which has the added benefit that it then appears in the storyline selection list so more people will find it. Another would be to only allow the sidequest to trigger if the year is at least 1812. (You can't check for the year being exactly 1812 because by the time the player reaches level 10, it might be 1813 or later.)
Otherwise we'll need to figure out a way to lock the date for models with an active 'model.storytitle' line in their definitions. José Joaquím Almeida isn't the only FreePlay character who will look odd if the player changes the year after selecting the character - imagine playing Francis Drake in the "Golden Age of Piracy" period, doing the "Angelique Moulin" sidequest, and digging up his own sword.