What time was it 12 hours ago? Look at your clock, keep the exact same hour and minutes, and flip AM to PM or PM to AM. At 6:50 AM, the answer is 6:50 PM yesterday.
What time will it be 10 hours from now? Add ten hours to the time on your clock and leave the minutes as they are. At 7:10 AM, the answer is 5:10 PM the same day.
Wondering how long until 7 AM? Check the clock: if it reads 5:20 AM, you have 1 hour and 40 minutes left. If 7 AM has already gone by, the countdown simply rolls forward to tomorrow morning instead.
Trying to work out how long until 6:30 AM? Look at the clock first. Before 6:30 AM today, subtract now from 6:30 AM. Once 6:30 AM has already gone by, count forward to 6:30 AM tomorrow instead. That single rule covers every case.
Planning something six weeks out? What date is 6 weeks from today is really just a counting question: take today's date, add 42 days, and read off the result. There is no month-guessing involved, because a week is always exactly seven days, no matter which month it crosses.
How long until 6 AM depends only on what your clock shows right now. If it's still before 6:00 AM, count forward to it. If 6 AM has already gone by, the countdown simply resets and points at tomorrow's 6 AM instead.
What time was it 9 hours ago? Subtract nine hours from the time on your clock and leave the minutes as they are. At 7:25 PM, the answer is 10:25 AM the same day.
What time will it be 8 hours from now? Add eight hours to the time on your clock and leave the minutes exactly as they are. At 7:10 AM, the answer is 3:10 PM the same day.
Wondering what date is 4 weeks from today? Grab a calendar and count forward 28 days from right now. Four weeks is always exactly 28 days. A week never changes length. The weekday stays the same too. Whatever day it is today, that is the weekday you land on four weeks out.
How long until 3:00 AM depends only on the clock in front of you right now. If it is 1:50 AM, the wait is 1 hour and 10 minutes. If it is 9:15 PM, the wait is 5 hours and 45 minutes, because the clock has to roll past midnight first. Once 3:00 AM has already gone by for the day, the countdown simply resets and points to tomorrow's 3:00 AM instead.