What date is 2 days from now? That is the day after tomorrow. Take today's date, add two days, and you land on it. It is one day further out than tomorrow. That is just far enough away to plan around, without feeling like a distant date on the calendar.
What time was it 13 hours ago? Take thirteen hours off your current clock reading and keep the minutes exactly where they are. At 8:20 AM, that lands on 7:20 PM the evening before.
What time will it be 14 hours from now? Add fourteen hours to the time on your clock and leave the minutes untouched. At 5:50 AM, the answer is 7:50 PM the same day.
How long until 3:25 AM changes with every glance at the clock. If it is currently 1:05 AM, you still have 2 hours 20 minutes ahead of you. If it is already 3:15 AM, only 10 minutes remain. Once 3:25 AM has come and gone for the night, the countdown quietly resets and points toward the following night instead.
How long until 3:23 PM changes with every tick of your own clock. If your day hasn't reached 3:23 PM yet, take your current time away from 3:23 PM and you have your answer. If the clock has already swept past it, the wait simply points ahead to 3:23 PM tomorrow instead.
Trying to work out what date was it 2 days ago? Take today's date and step back two full calendar days. If today is Thursday, two days ago was Tuesday, the same week. No hours or minutes are involved, only whole days. So the answer never depends on what time it is right now, only on what today's date is.
How long until 3:15 PM comes down to one quick step. Take 3:15 PM and subtract your clock right now. Say it is 12:40 PM. That leaves 2 hours and 35 minutes to go. Once 3:15 PM slips by for the day, the question simply points forward. It now means 3:15 PM tomorrow.
What time will it be 13 hours from now? Add thirteen hours to the time on your clock and leave the minutes untouched. At 6:05 AM, the answer is 7:05 PM the same day.
What time was it 10 hours ago? Pull ten hours off your current clock reading and leave the minutes exactly as they are. At 7:35 AM, that lands on 9:35 PM the night before.
What date is 1 day from now? That is simply tomorrow. Take today's date, add one day, and you land on tomorrow's calendar square. Most months, that just means the day number goes up by one. Near the end of a month, it rolls the date into the first of the next month instead.