"They go to the bank on Thursday."
Translation:Mereka ke bank di hari Kamis.
'Di' shouldn't be used as a word for 'on' in this context. You should use 'pada'.
i've noticed that so far 'di' is always used with days of the week, but outside of duolingo i have seen 'pada'.
is there a general rule as to when you choose one of these words over the other?
This sentence should also be translated as "Mereka pergi ke bank di/pada hari Kamis."