Here are the school schedules translated to English from the Finnish National Agency for Education- Opetushallitus. The schedules include the dates of the schools working days and holidays in mainland Finland.
Parents would usually struggle in getting babysitters during these holidays. Having a detailed schedule early on makes it easier to plan what to do during these holidays. Companies are often flexible to parents with small children and grant them holidays during these periods. If the parents need to stay at work, there are usually day camps for kids in school premises. The Lutheran church, and sport and youth associations typically organize these events and at the same time, you can always contact the parent associations from school.