Klingon does not mark tense on its verbs, so without any clarifying context a sentence could be in the past, present or future. 'IH tlhIngan doesn't just mean The Klingon was handsome; it means The Klingon was/is/will be handsome. You can use it to mean any of those things. Presumably your listener will know which you mean.
This doesn't always work in the reverse direction. You can't say any old tense will collapse into a tenseless Klingon sentence. English doesn't mark its verbs for something that Klingon does have, aspect. For instance, the English sentence I saw the officer in the room is in the simple past tense, but it has a perfective sense: perfective means the action is a completed and not looked at as unfolding over time. English doesn't mark this on the sentence, but Klingon does, with the suffix -pu' perfective. pa'Daq yaS vIleghpu'. If you left off the -pu', you might be talking about seeing the officer in the room once a day or something, something not completed. (This sentence and its translation appears in The Klingon Dictionary.)
Unfortunately, this course doesn't handle the Klingon perfective aspect very well. You may often come across sentences that ought to be perfective that the software won't let you use perfective on. You just have to do what the course says, even when it's wrong.
Jeremy remains unconvinced. He cannot account for the complete alignment of this (correct) definition of perfective and the fact that everything Okrand has ever written in Klingon conforms to it and not to the grammar used in this course. We like to be passive-aggressive about it at each other.
I do not agree that Dr. Okrand or his canon conform so well to David's understanding, but I'm not ready to comb through the canon and find the counter examples.
I do appreciate that David comes here to share where his view of the intricacies of Klingon grammar differ from the creators of this course. I think it's valuable for the learners to learn the different perspectives. But I will always argue when David says we're wrong or his way is the only way.
David and I both have decades of experience with the language and we have each had multiple direct conversations with Dr. Okrand yet we have come to differring interpretations. Still I will admit that aspect is a more complex concept than this software is prepared to deal with well and that we have simplified it somewhat.
I'm not ready to comb through the canon and find the counter examples.
I have done so. I do not recall ever finding any. Occasionally one finds the use of a perfective suffix where the rules disallow them, but never the lack of a suffix (or rIntaH) where the expression is clearly perfective.