Without going too deep into the complex nature of time, we can safely say that time flies - tempus fugit!
Therefore, inspired by informal representations of duration like this EveXL uses the [<- INTERVAL-ID ->] notation to apply conditions on interval durations.
For instance, the following expression should be read as
We can compare interval durations. For example, the following expression means that:
This will match an interval of red readings shorter than another interval of blue readings.