What this calculator does
How long until 3:15, or any other specific time of day, is a question of subtracting the current time from a target clock time, then rolling forward to tomorrow if that time has already passed today. This calculator does exactly that for any time entered.
The target time is not fixed to any one moment: entering 15:15 answers how long until 3:15 pm, and entering any other time answers the same question for that time instead, whether it is how long until 3pm, midnight, or any other point on the clock.
The formula
Take the target time entered and build today's date at that hour and minute. If that moment is still ahead of the current time, the countdown is simply target minus now. If it has already passed today, the same target time tomorrow is used instead, and the countdown runs to that.
| Term | Meaning |
|---|---|
| Target time | The clock time being counted down to, entered as hours and minutes. |
| Current time | The time right now, taken from the device running the calculator. |
| Rolled to tomorrow | What happens when the target time has already passed today: the countdown switches to the same time on the next day instead. |
The inputs explained
| Field | What to enter |
|---|---|
| Target time | The clock time to count down to, in 24-hour or 12-hour format depending on your device. |
When to use it
Checking how long until 3pm or another specific hour
A meeting, a break, or an event starting at a fixed clock time, rather than a fixed date and time far in the future, is exactly what this calculator is built to count down to.
Working out how long until 3:15 for a scheduled call
A call or appointment set for a specific time today needs a live countdown rather than a static duration, since the answer changes by the minute as the target approaches.
Timing a task against the next occurrence of a clock time
A recurring daily target, such as a train departure or a shop's opening time, is always "the next time this clock time comes around", which this calculator handles by rolling to tomorrow automatically once today's occurrence has passed.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How long until a range of common target times, from now?
A range of target times, each counted down to from the moment this page is generated.
| Target time | Time remaining | In minutes | Target time |
|---|---|---|---|
| 09:00 | 0 h 9 min 52 s | 9.9 | 09:00 (today) |
| 12:00 | 3 h 9 min 52 s | 189.9 | 12:00 (today) |
| 15:00 | 6 h 9 min 52 s | 369.9 | 15:00 (today) |
| 15:15 | 6 h 24 min 52 s | 384.9 | 15:15 (today) |
| 18:00 | 9 h 9 min 52 s | 549.9 | 18:00 (today) |
| 21:00 | 12 h 9 min 52 s | 729.9 | 21:00 (today) |
Questions
How long until 3:15?
That depends entirely on the current time, which is why this is a live calculator rather than a fixed answer: enter 15:15 as the target time above and the exact countdown from right now is shown immediately.
What happens if the time I enter has already passed today?
The calculator automatically counts down to that same clock time tomorrow instead, so the countdown never shows a negative or already-passed result.
Can I use this for a time that is not 3pm?
Yes. The target time is a normal, fully adjustable input: enter any hour and minute, from midnight to 11:59 pm, and the calculator counts down to that time in exactly the same way.
How is this different from the countdown calculator?
This page counts down to a specific time of day only, rolling to tomorrow if needed, with no date to enter. The countdown calculator counts down to a specific date and time together, for a deadline or event further in the future than the next occurrence of a clock time.
For a countdown to a specific date, not just a time of day, see the countdown to a date calculator. For the day of the week and week number of any date, see the day of the week calculator.