From now on, Peter -Paul's fasting began - what should he know who is going to fast

From today, Peter-Paul's fast began. Compared to the Lent, this fast is lightweight and fishes (except Wednesday and Friday). The duration of the fasting of Peter-Paul is variable and the Pentecost, which in turn depends on Easter and celebrates the 50th day of Easter. Fasting begins in one week after Pentecost ....