Perception of time is your definition of consciousness?
Do you instead mean memory of autobiographical events ?
Patient H.M lost his ability to form new memories of his experiences. (Starting after a brain surgery removed part of his memory centers as a kid). Would that count as losing "consciousness"?
People with dementia also lose their ability to form new memories. Though the complete loss of this ability is after the disease has progressed to severe levels.
People with Korsokoff disease. Sometimes called "locked in time" is also a disorder where new memory is disrupted so the individual often has no understanding that many years have passed. But they also suffer from a loss of time. Possibly because the amnesia is so extreme and complete.
This is why I say that time perception is part of memory.
People with Korsokoff are often distressed when they see their aged face in a mirror. Because to them, they have aged 20 years without experiencing the passage of 20 years.
Would you say these people are not conscious ?
You get why even defining consciousness is not particularly easy.
But we can't develop explanations without a specific defined phenomenon that can be measured or identified in some way.