When do I know if I should look for assisted living or just senior housing for my 84 year old Mom who has no concept of time?

Your profile says Mom has dementia. I think that completely rules out a senior apartment or any kind of independent living.

Dementia progresses. Even if she is fine in assisted living now, that may not last long. If her doctor thinks ALF is appropriate now, try to ensure it is in a facility that has increasing levels of care available. Moving to an entirely different facility would be hard later. Depending on the kind of dementia she has and the range of her impairments, a "memory care" facility may be appropriate now and also for some time to come.

Discuss the options with her doctor, and also talk frankly with the administrator of any facilities you are considering. They need to know here diagnosis and her current symptoms in order to determine if they can provide the services she needs.

if she has no concept of time id say there isnt any rush.
glad i got that out of my system, ill sleep better..

Talk to her MD about her options, she sounds like a nursing home candidate or a memory care facility, not just assisted living.