This keyword evaluates to the number of milliseconds passed since the passage was displayed. Its main purpose is to be used alongside Changer such as (live:) or (link:). (link:"Click")[(if: time > 5s)[...]], for instance, can be used to determine if 5 seconds have passed since this passage was displayed, and thus whether the player waited 5 seconds before clicking the link.

When the passage is initially being rendered, time will be 0.

time used in (display:) macros will still produce the time of the host passage, not the contained passage. So, you can't use it to determine how long the (display:)ed passage has been present in the host passage.