Could aliens have a completely different sense of time?

Yes—it's plausible that aliens could have a very different sense of time, but we can’t know for sure.

Time perception depends on biology, environment, and cognition. On Earth, animals with faster nervous systems can react on much shorter timescales than humans, so an alien species with very different neural processing could experience the world as slower or faster than we do. A hyper-fast metabolism might make human movement seem agonizingly slow, while a massive, cold-dwelling, or silicon-based lifeform might experience human lifetimes as almost a blink.

Their planet or habitat could also shape how they think about time. A world with unusual day-night cycles, long seasons, or no obvious solar cycle at all might lead to very different concepts of daily and seasonal time. Life in deep subterranean oceans or in environments with no clear sun or seasons might evolve without those cues entirely.

Structure matters too: a decentralized brain or hive-mind consciousness could process time across multiple nodes at once rather than as a single linear stream.

Physics matters as well: relativity means that time can pass at different rates depending on speed and gravity, though that’s about physical time rather than perception.

So the short answer is yes: alien time perception could be very different from ours, but any specific example is still hypothetical.