When a noun is a temporal noun like diena (day) or kartas (a time), time is expressed through the accusative or instrumental case. You learned this in the previous lesson.

However, if a noun is not a temporal noun, for example: pamoka (lesson), paskaita (lecture), karas (war) or any other noun that you wish to express time with, then you must use the locative case:

Šioje pamokoje mokytojas kalba, o mokiniai klauso. In this lesson the teacher is speaking and the students are listening.
Paskaitoje dėstytojas žiūri į studentus. In the lecture the lecturer is looking at the students.
Mes esame kare. We are at war.