An elderly man admitted to hospital cannot say what day or month it is, but can correctly identify that he is in a hospital and can correctly name his wife when she visits. What is the underlying finding, and what does the pattern tell you about its severity?

This is disorientation, currently affecting time but not yet place or person: loss of accurate awareness of time, place, or person, typically lost in that specific order as a disturbance of consciousness worsens, with orientation for time lost most easily since it depends on continuously tracking events that mark the passage of time, easily disrupted by an unfamiliar hospital routine. It is not disorientation affecting all three equally, since place and person are both intact here, and orientation for place and especially person are retained longer, as the surroundings and other people themselves supply identifying clues. It is not perplexity, which is a subjective sense of bewilderment rather than actual loss of orientation, and basic orientation is typically preserved in perplexity. And it is not anterograde amnesia specifically, which concerns the inability to lay down new memories, not disorientation to time as such, though the two can co-occur.