Pursuant to Art. 335c, para. 1, of the Swiss Code of Obligations (OR), the employment relationship may be terminated after the probationary period has expired during the first year of service with one month’s notice; during the second through ninth years of service, with a notice period of 2 months; and thereafter, with a notice period of 3 months, in each case effective at the end of a month.
These notice periods may be modified by written agreement, a standard employment contract, or a collective bargaining agreement; however, they may be reduced to less than one month only by a collective bargaining agreement and only for the first year of employment (Art. 335c, para. 2, OR).
Under the law, notice of termination takes effect at the end of a month. However, this may be modified by contractual agreement, and any day may be designated as the effective date of termination, provided that the notice period is observed.
See the following link: https://www.seco.admin.ch/seco/de/home/Arbeit/Personenfreizugigkeit_Arbeitsbeziehungen/Arbeitsrecht/FAQ_zum_privaten_Arbeitsrecht/kuendigung.html (under the question “What notice periods does the law provide for?”).
One more special note:
If a notice of termination is served during the first year of employment, the one-month notice period applies, even if the notice period does not expire until the second year of employment.