Law / Notice period Poland (job termination) - does 'one month' equal to four weeks? [13]

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NOTICE PERIOD CALCULTION

Hello Forum!

I started working in Poland with a company on 01.12.2017. I am curious to know what would be my notice period if I decide to resign:

1. In August 2020.

2. In September 2020.

Thank you in advance for your answer.

P.S - I know the notice period is 3 months after employee is 3 years old in the company but I don't know how it is calculated.