They offer 50%/70% or seasonal part-time. With 50 and 70% you can choose what they call a split month or split week. from what I understand, the split month gives you the part time days together and the split week gives you the part time days each week (block).One my friend is on the 50% contract, and works fri/sat/sun only. With seasonal part-time, you work full-time jun/july/aug/sept and part-time the rest of the year.
As mentioned before, you have to be in the company 1st, then apply for part-time, it can take couple of months or years depending on your base and how many people are on the waiting list for the part time.