YOU SAID:
i babysat for my neighbor yesterday
INTO JAPANESE
私は昨日隣人のためにbabysatしました
BACK INTO ENGLISH
I did babysat for my neighbor yesterday
INTO JAPANESE
私は昨日隣人のためにbabysatをしました
BACK INTO ENGLISH
I did babysat for my neighbor yesterday
You've done this before, haven't you.