celebrating certain holidays/events on different dates

[ThePotatoGuy]

might be more realistic to allow players to celebrate certain events on dates other than the primary one.
Or maybe even not celebrate an event at all?

For example:

1. 2 weeks before vday, have Monika prompt the user about vday.
2. Have her ask the user what both of you are going to do that day.
3. User options could include:
   • it's a surprise
   • nothing
   • actually lets celebrate different day
   • etc...
4. Picking the different day option would allow the user to pick a date that works for them.
5. Appropriate vday related topics then should adjust to the new date

This can get very complicated and might be too much for what its worth.

Additionally, we might need to finish #792 first to make this more feasible