Hi Nick, I wish that your studying Japanese goes well. If I hear / read "に in this context, I would expect the following verbs like "おこなわれます / ひらかれます" instead of "です" But this can be possible and sound natural; 「つぎの かいぎ は いつ おこなわれますか」 「きんようび(に)です」 「では、また きんようび に（あいましょう）」 In the case above, "おこなわれます" is just hidden after "に". And you can also omit following "です" and say 「きんようびに」 I think it possible because we already heard the verb "おこなわれる" in the question.

Hi Nick. に is a particle (time particle). We use particle before verb, meaning it must be followed with a verb. For example. かいぎはきんようびにあります。 かいぎはきんようびになります。 かいぎはきんようびにおこなわれます。 If you want to make it brief , replace the particle にwith です and then full stop -> かいぎはきんようびです。です is an auxiliary verb. If you use にas a time particle, there is a special emphasis at the time in your sentence. http://www.guidetojapanese.org/particles2.html You can learn further about this in japanese morphology. Hope it helps.