To find the time some hours from now, add the hours to the current time and subtract 24 each time you pass midnight — each 24 hours moves the date forward one day. For example, at 9:00 AM, 5 hours from now is 2:00 PM, 13 hours from now is 10:00 PM and 18 hours from now is 3:00 AM tomorrow. The calculator above uses your own clock and shows the result in 12-hour and 24-hour time with the weekday and date.
It also works backwards (“what time was it 15 hours ago?”) and as a countdown to midnight or any clock time. All you need is the number of hours and minutes; the start defaults to your device clock.
How to use this calculator
- Pick Time from now / ago to add or subtract time, or Time until a clock time for a countdown.
- Leave the start on Now (your device clock), or choose a date and time to start from.
- Enter days, hours and minutes. Use days for long spans such as 100 hours (4 days 4 hours).
- Choose From now or Ago, and read the time, the 24-hour time, the date and whether you cross midnight.
- For a countdown, set the target time (midnight is 00:00). If that time has already passed today, the count runs to tomorrow.
How it's calculated
- New time = current time + hours × 60 + minutes. Anything past 24:00 rolls into the next day; anything before 00:00 rolls back to the previous day.
- Crossing midnight: the number of whole days the result moves is shown as “tomorrow”, “yesterday” or “2 days later”.
- Time until = target time − current time, plus 24 hours if the target has already passed today.
- Elapsed time, not clock time. The calculator adds real elapsed hours, then shows what your clock will read. Near a daylight saving change the two differ by an hour (see below).
The “now” comes from your own device. NIST keeps the official U.S. time, UTC(NIST), and says it agrees with the Naval Observatory's UTC(USNO) to within 20 nanoseconds (NIST, About time.gov). Phones and computers that set their clock automatically sync to a network time source; if yours is set manually, check it against time.gov.
Quick rules for hours from now
- 12 hours from now = the same number, AM ↔ PM swapped (9:00 AM → 9:00 PM).
- 24 hours from now = the same time tomorrow.
- Between 12 and 24 hours: go back (24 − hours) and make it tomorrow. 18 hours from now = 6 hours earlier tomorrow; 20 hours = 4 hours earlier tomorrow.
- Hours ago, between 12 and 24: go forward (24 − hours) and make it yesterday. 15 hours ago = 9 hours later yesterday; 23 hours ago = 1 hour later yesterday.
- 48, 72, 100 and 120 hours are 2 days, 3 days, 4 days 4 hours and 5 days.
Worked examples
18 hours from now
At 2:30 PM: 14:30 + 18:00 = 32:30. Subtract 24 hours to get 08:30, and the day moves forward one: 8:30 AM tomorrow.
What time was it 15 hours ago?
At 10:20 AM: 10:20 − 15:00 = −4:40. Add 24 hours to get 19:20: 7:20 PM yesterday.
What time will it be in 15 minutes?
At 11:50 AM: 50 + 15 = 65 minutes, which is 1 hour 5 minutes, so 12:05 PM. Note that it is now PM — noon was crossed.
How long until midnight?
At 7:40 PM: 24:00 − 19:40 = 4 hours 20 minutes.
100 hours from now
100 hours = 4 days and 4 hours. At 9:00 AM on a Monday, 100 hours from now is 1:00 PM, 4 days later, on Friday.
Hours from now and hours ago
Filled in from your device's clock when the page loads (the times update every minute). Each cell shows the clock time and the day.
| Hours | From now | Ago |
|---|---|---|
| 1 hour | – | – |
| 2 hours | – | – |
| 3 hours | – | – |
| 4 hours | – | – |
| 5 hours | – | – |
| 6 hours | – | – |
| 7 hours | – | – |
| 8 hours | – | – |
| 9 hours | – | – |
| 10 hours | – | – |
| 11 hours | – | – |
| 12 hours | – | – |
| 13 hours | – | – |
| 14 hours | – | – |
| 15 hours | – | – |
| 16 hours | – | – |
| 17 hours | – | – |
| 18 hours | – | – |
| 19 hours | – | – |
| 20 hours | – | – |
| 21 hours | – | – |
| 22 hours | – | – |
| 23 hours | – | – |
| 24 hours | – | – |
| 30 hours | – | – |
| 36 hours | – | – |
| 48 hours | – | – |
| 72 hours | – | – |
| 100 hours | – | – |
| 120 hours | – | – |
Minutes from now and minutes ago
Every 5 minutes up to an hour, plus 90 minutes, 1 hour 40 minutes, 1 hour 45 minutes and 2 hours 30 minutes. For other values, type the minutes into the calculator.
| Minutes | From now | Ago |
|---|---|---|
| 5 minutes | – | – |
| 10 minutes | – | – |
| 15 minutes | – | – |
| 20 minutes | – | – |
| 25 minutes | – | – |
| 30 minutes | – | – |
| 35 minutes | – | – |
| 40 minutes | – | – |
| 45 minutes | – | – |
| 50 minutes | – | – |
| 55 minutes | – | – |
| 60 minutes | – | – |
| 90 min (1 hour 30 minutes) | – | – |
| 100 min (1 hour 40 minutes) | – | – |
| 105 min (1 hour 45 minutes) | – | – |
| 150 min (2 hours 30 minutes) | – | – |
Time until common clock times
Time left until the next time your clock shows each time. Midnight means 12:00 AM (00:00) at the start of the next day.
| Until | Time left | Minutes |
|---|---|---|
| Midnight (12:00 AM) | – | – |
| 5:00 AM | – | – |
| 6:00 AM | – | – |
| 6:30 AM | – | – |
| 7:00 AM | – | – |
| 8:00 AM | – | – |
| 9:00 AM | – | – |
| Noon (12:00 PM) | – | – |
| 3:00 PM | – | – |
| 3:45 PM | – | – |
| 5:00 PM | – | – |
| 6:00 PM | – | – |
| 9:00 PM | – | – |
| 10:00 PM | – | – |
| 11:59 PM | – | – |
12 AM, 12 PM, noon and midnight
This calculator shows midnight as 12:00 AM and noon as 12:00 PM, as phone and computer clocks do. NIST points out that “12 a.m.” and “12 p.m.” are strictly ambiguous, and recommends the 24-hour clock — 0000 for midnight at the start of a day, 2400 for its end — or writing 11:59 p.m. or 12:01 a.m. when a deadline matters (NIST, Times of day FAQs). The 24-hour result in the calculator removes the doubt. To convert other times, use the military time converter.
Daylight saving time
Under federal law, U.S. daylight saving time starts at 2:00 a.m. local time on the second Sunday of March and ends at 2:00 a.m. on the first Sunday of November (15 U.S.C. § 260a). In March the clock jumps from 2:00 to 3:00, so that day has 23 hours; in November it falls back from 2:00 to 1:00 and the day has 25 (NIST).
- 24 hours after noon on the Saturday before the spring change, the clock reads 1:00 PM on Sunday, not noon.
- 24 hours after noon on the Saturday before the fall change, it reads 11:00 AM on Sunday.
- States may opt out and stay on standard time all year. NIST lists Hawaii, Arizona (except the Navajo Indian Reservation), American Samoa, Guam, Puerto Rico and the U.S. Virgin Islands as not observing DST. The calculator follows your device's time zone settings, so it handles both.
Common mistakes
- Forgetting the date change. Anything that passes midnight lands on a different day — “9 hours from now” at 8 PM is tomorrow morning.
- Mixing up 12 AM and 12 PM. 12 hours after 11 AM is 11 PM, but 1 hour after 11:30 AM is 12:30 PM (afternoon), not AM.
- Treating minutes as decimals. 1.5 hours is 1 hour 30 minutes, not 1 hour 50. 100 minutes is 1 hour 40 minutes.
- Time zones. The result is in your device's time zone. If the other person is in another zone, convert afterwards; the U.S. and its territories use nine standard time zones (USNO).
For spans of days and weeks rather than hours, use the days and weeks from today calculator; to total the hours on a time card, use the work hours calculator.
Frequently asked questions
What time will it be in 15 minutes from now?
Add 15 to the minutes; if that passes 60, move to the next hour. At 9:50 AM it will be 10:05 AM; at 11:50 PM it will be 12:05 AM tomorrow. The calculator above reads your device clock and shows the exact time.
What time is 18 hours from now?
18 hours is 6 hours short of a full day, so it is 6 hours earlier than now, tomorrow. At 9:00 AM today, 18 hours from now is 3:00 AM tomorrow; at 9:00 PM it is 3:00 PM tomorrow.
12 hours from now is what time?
The same clock number with AM and PM swapped. 9:00 AM becomes 9:00 PM; 9:00 PM becomes 9:00 AM tomorrow.
From now, when is 24 hours?
The same clock time tomorrow — 24 hours after 9:00 AM is 9:00 AM tomorrow. The one exception is a daylight saving change: across the spring change the clock reads one hour later, and across the fall change one hour earlier, because clocks jump at 2:00 a.m. local time (15 U.S.C. 260a).
What time was it 15 hours ago?
15 hours ago is 9 hours later than now on the clock, yesterday. At 9:00 AM, 15 hours ago was 6:00 PM yesterday; 13 hours ago was 8:00 PM yesterday.
How long until midnight?
Subtract the current time from 24:00. At 9:15 PM there are 2 hours 45 minutes until midnight; at 6:00 PM, 6 hours. The "Time until" mode counts down from your device's clock.
Is midnight 12 AM or 12 PM?
NIST calls 12 a.m. and 12 p.m. ambiguous, because noon is neither before nor after noon. On digital clocks midnight shows as 12:00 AM and noon as 12:00 PM. For clarity, NIST suggests 24-hour times — 0000 for midnight at the start of a day and 2400 for the end — or writing 11:59 p.m. or 12:01 a.m.
Does daylight saving time change the answer?
Only if your span includes 2:00 a.m. local time on the second Sunday of March or the first Sunday of November, when U.S. clocks move forward or back one hour (15 U.S.C. 260a). This calculator counts real elapsed hours using your device's time zone rules, so its result already reflects the change. NIST lists Hawaii, Arizona (except the Navajo Indian Reservation), American Samoa, Guam, Puerto Rico and the Virgin Islands as not observing DST.
Sources & method
- NIST — About time.gov (official U.S. time, UTC(NIST))
- NIST — Times of day FAQs (12 a.m., 12 p.m., noon and midnight)
- NIST — Daylight Saving Time (DST)
- 15 U.S.C. § 260a — Advancement of time (Legal Information Institute)
- U.S. Naval Observatory — U.S. time zones
Results are estimates for general information. Found an error? It helps everyone — see our methodology.