Not sure this helps... Check this out with google translator:
Compulsory military service related mainly to men, (even though the law explicitly allows for the possibility of accepting volunteers for military service) from 21 to 60 years of age residing in the Second Republic [...]
Compulsory military service, however, were covered only men in the period from January 1 this year, which ends 21 years until the end of the calendar year in which they turn 23 years old. However, in case of mobilization and war were allowed reduction of this period to 18 years. In the event of war and mobilization to the call of district authorities also they have to appear citizens aged 18-23 years, who are already performing military service.
Conscripts were eligible for category A (capable), B (temporarily incapable - only for 21-22 year olds), E (totally incapable of military service), C (unfit to arms) or D (capable of auxiliary military service) .
From the collection in 1938. Military service was to be:
a) in the cavalry and artillery - 25 months
b) in other formations WP - 24 months
c) MWP - 27 months
dawnygarnizonpoznan.fora.pl/garnizon-poznan-1919-1939,44/warunki-poboru-do-wojska-polskiego-w-ii-rp,442.html
The law was changed in 1967 - the new act came into force.