"I was reading that book last night."
Translation:wa'Hu' ram paqvetlh vIlaDtaH.
That's an excellent question and one that this course is not well equipped to deal with. The -taH suffix does indicate "continuous aspect". Klingon does not have tenses so it could be past, present, or future. As stated in The Klingon Dictionary:
Klingon does not express tenses (past, present, future). These ideas come across from context or other words in the sentence (such as wa'leS tomorrow). The langauge does, however, indicate aspect: whether an action is completed or not yet completed, and whether an action is a single event or a continuing one.
The -taH suffix is the method by which the language indicates that an action is ongoing. I will admit that the continuous aspect does not line up exactly with the use of the progressive tenses in English. However, to keep things simpler in this course which does not use context, we have equated the Klingon continuous aspect with the English progressive tenses. Thus vIlaDtaH would have accepted translations of, "I was reading it," "I am reading it," or, "I will be reading it."
It occurred to me that since this is early in the course, we might not have explained how to use the time stamps in the Tips. That's an important omission. The Skill that has this sentence is where we first introduce time stamps, so I have added a section about them to the Tips from this Skill. It may take a week or so for the new Tips to appear.
The new section says:
Since Klingon verbs lack tense, a common way to indicate the tense of a sentence is to note the time frame of the action at the start of the sentence. These are often called "Time Stamps". We use them in English, too:
Tomorrow I will fight the enemy.
"Tomorrow" is a time stamp. In Klingon the word for "tomorrow" is wa'leS:
wa'leS jagh vISuv.
In English, time stamps can be moved around in the sentence and it is also possible to say, "I will fight the enemy tomorrow." This is NOT true in Klingon. In Klingon the Time Stamp must be part of the beginning of the sentence and must be before the object, if there is one (which also means before the verb, whether there is an object or not). As you learn more about Klingon grammar, you will see that there are also other elements that will be part of the beginning of the sentence before the object.