It is not that you lose track of time. It is that time never registered as something moving in the first place.
People assume time blindness means forgetting to look at the clock. Most of us look constantly. The number is right there, and it still does not land. You read 4:15, you understand 4:15, and nothing in your body responds to it. Twenty minutes later you read 4:35 with exactly the same flat non-reaction, and somewhere in between an hour of your evening quietly left the building.
That gap between knowing the time and feeling the time is the whole condition. It shows up most often in ADHD, and it also shows up in autistic people, in people with brain injuries, and in anyone deep enough in a depressive episode that days stop having edges.
From the outside it looks like carelessness. You said you would leave at seven and you left at seven forty. You said this would take an hour and it took four. The obvious reading is that you did not care enough to try.
From the inside there was no moment where it felt like forty minutes had gone by. There was a moment that felt like a few minutes, and then the clock disagreed with you. This is why being told to "just watch the time" is such useless advice. The watching was never the missing part.
Time blindness is not a failure of effort. It is a difference in perception, and you cannot try harder at perception.
Forward, it makes starting impossible. A task with no felt duration is a task of unknown size. Unknown size feels enormous. So the dishes, which take eleven minutes, sit there for three days, because your brain has priced them somewhere near "an entire afternoon" and refuses to open the tab.
Backward, it makes stopping impossible. Once you are inside something absorbing, nothing interrupts. Not hunger, not the dark outside, not the meeting. Hyperfocus is often described as a superpower, and it can be, but the reason it wrecks schedules is that it removes the only internal signal most people rely on to come up for air.
An alarm is a wall at the end of a hallway you cannot see down. It tells you the time is up. It never tells you the time is going. So you spend the whole session with no sense of position, then get startled, and the startle itself is unpleasant enough that plenty of people stop setting alarms at all.
What actually helps is continuous, ambient, and requires no reading: something that is visibly less than it was a minute ago.
Almost everyone with time blindness has a private stack of evidence that they are unreliable. Years of being late, of underestimating, of the same disappointed tone from the same people. That stack is doing real damage, and it is worth saying plainly: a perceptual difference is not a character flaw. The goal is not to become someone who feels time normally. It is to put the information somewhere your eyes can reach it without your self-image getting involved.
Sundae turns a focus session into an ice cream that visibly melts, in real time, on screen and on your Lock Screen. Step away and it just naps: nothing withers and nothing is lost. There is a working one on the home page you can try in your browser, no install.