In English, every verb is tagged for the grammatical category called tense: past, present, or future. The sentence

necessarily happens at some time in the past, whereas

is necessarily happening right now.

The Lojban sentence

serves as a translation of either Example 2.87 or Example 2.88, and of many other possible English sentences as well. It is not marked for tense, and can refer to an event in the past, the present or the future. This rule does not mean that Lojban has no way of representing the time of an event. A close translation of Example 2.87 would be:

where the tag pu forces the sentence to refer to a time in the past. Similarly,

necessarily refers to the present, because of the tag ca. Tags used in this way always appear at the very beginning of the selbri, just after the cu, and they may make a cu unnecessary, since tags cannot be absorbed into tanru. Such tags serve as an equivalent to English tenses and adverbs. In Lojban, tense information is completely optional. If unspecified, the appropriate tense is picked up from context.

Lojban also extends the notion of “tense” to refer not only to time but to space. The following example uses the tag vu to specify that the event it describes happens far away from the speaker:

In addition, tense tags (either for time or space) can be prefixed to the selbri of a description, producing a tensed sumti:

(Since Lojban tense is optional, we don't know when he or she talks.)

Tensed sumti with space tags correspond roughly to the English use of “this” or “that” as adjectives, as in the following example, which uses the tag vi meaning “nearby”:

Do not confuse the use of vi in Example 2.94 with the cmavo ti, which also means “this”, but in the sense of “this thing”.

Furthermore, a tense tag can appear both on the selbri and within a description, as in the following example (where ba is the tag for future time):