It should have been kata "pada" instead of "katanya pada". you use "nya" as a pronoun ^^
"pada" is a time preposition, or what you guys, the English speakers known as "at" or "on" or "in". As Indonesian is really simple, we don't divide our time preposition as what you do in English. So you use only one preposition for all.
For examples:
at 3 pm ==> pada jam 3 sore
on saturday ==> pada hari sabtu
on 20th of June ==> pada tanggal 20 Juni
in 2015 ==> pada tahun 2015
when she came ==> pada waktu/saat dia datang (note here that in this case, "pada" works as emphasis, you can choose to omit "pada", but you cannot omit "waktu/saat")
The most common mistake that I often found from non-native Indonesian speakers is that, you guys use "di", which is a place preposition, instead of "pada". I suppose it's because in English you use the same prepositions for time and place. even though in some situations they can replace each other, but mostly they cannot. So unless your grammar is at advanced level, it's better for you to just use "pada" for time preposition.
note that "pada" and "kepada" is different, because "kepada" means "to"
I Hope it helps. Let me know if you have more questions ^^