I am concerned about a term in my contract:

'Employee and employer can terminate this contract until the end of first year by giving 30 days notice prior to the end of the contract(August). After the first year, either party shall give written notice of termination in January.'

Is it legal according to Swiss law to have such a term during the first year, which then changes? What does the Swiss say regarding the notice of leave?

Yes. It is in fact standard if not specified otherwise in the contract. (See here).

I say a 12 month notice period (every January if I don't misunderstand you?) is exceptionally high!


Edit: The January thing makes me wonder if you are speaking of a convention collective / Gesamtarbeitsvertrag? If yes it probably means that the contract can be modified every January, after negotiations between your union and your employer, and you probably still have a shorter notice period than 12 months.