working days

[Makhini]

what's the number of maximum working days you should not exceed per month ?
is it ok that my employer asks me to work 28 days every month in a permanent job?

[Piet]

what's the number of maximum working days you should not exceed per month ?
is it ok that my employer asks me to work 28 days every month in a permanent job?

No that is not ok, but... it mainly depends on the collective labor agreements valid for your job, if there is none, you're still entitled to free days in a month and weekends, also remember you earn holidays and holiday money every hour you work, this accumulates and the employer must allow you to take your holidays and pay your holiday money.
28 days work in a month, means overtime, this earns you extra time off, however it is not allowed to do this structurally, it must be an exception..
(as far as my knowledge of labor law stretches, we have another forum member here that is very much skilled in the Finnish law, you might want to wait hers/his response to your post).

But this also depends on your contract, I have always found these zero hour contracts a form of slavery because you need to be ready to work but you do not get paid for your time on standby, while you should.

If you believe you are treated unfairly and you are a low wage worker, you might be eligible for state paid legal assistance, you can inform at "oikeusaputoimisto" if someone there can give you free advice, (initial meeting or phone call).
https://www.oikeuspalveluvirasto.fi/en/home/

Welcome to Finland where the current government has weakened the rights of the worker, threatens the worker with deportation when fired, and gives the employer a way to blackmail the worker in abiding by his wishes and demands, under the threat of unemployment and said deportation. Modern slavery of the rich, and at the same time push their own poor and low wage earners further into poverty...

[Makhini]

Useful and elaborated feedback.
Thank you very much @Piet