Why the iPhone Timer app displays a fake time

The tidbit about it displaying 1 even if there is 0.01 left is interesting though. Makes sense.

They would round it up to 60, the format it to be 01:00.

Surely one shouldn't round _after_ splitting the time into minutes and seconds.

You floor() or ceil() the time, depending on if you're counting up or down, to the lowest unit your timer is showing, then you display it and in the process split it into hours, minutes etc.

So ceil(59.51s) = 60s, which is then converted to 0h 1m 0s for display.

What?

> with rounding up it's even worse resulting in 1:01:51

Huh?

If you are making some kind of timer, you first should convert the time to pure seconds, or in whatever the smallest unit is that you care to deal with (milliseconds?). It is only at that point that the data is ready for any kind of arithmetic (for example, to subtract 1 second). Then, when you wish to display it, you first convert it.

For example, if the user sets your timer to 2 minutes, you would convert "2:00" to 120 seconds. Then you subtract 1 second. Now the internal value is 119. Then you convert back to the display format: "1:59". But be sure to keep "119" in some internal variable, for the next change.

    <form name=f>
        <input type=number name=h min=0 max=99 value=0>
        <input type=number name=m min=0 max=59 value=00>
        <input type=number name=s min=0 max=59 value=00>
        <input type=submit value=Start>
        <output name=r></output>
    </form>

    <script>

    document.forms.f.addEventListener('submit', function (ev) {

        ev.preventDefault();

        let f = ev.target,
            s = Number(f.h.value * 60 * 60) +
                Number(f.m.value * 60) +
                Number(f.s.value);

        function show(f, s) {

            let h = Math.floor(s / 60 / 60);
            s -= (h * 60 * 60);

            let m = Math.floor(s / 60);
            s -= (m * 60);

            m = String(m).padStart(2, '0');
            s = String(s).padStart(2, '0');

            f.elements.r.value = [h, m, s].join(':');
        }

        show(f, s);

        if (f.timer) { clearInterval(f.timer); }
        f.timer = setInterval(function () {
            if (0 === s) { clearInterval(f.timer); return; }
            s -= 1;
            show(f, s);
        }, 1000);
    });

    </script>

That doesn't really work for a countdown timer though since the last second would then display as zero, which is nonsense for 'time remaining'. You have to round up, always.

The Android 9 countdown works intuitively, it takes a second to decrement from 5 to 4 and sounds the alarm exactly at 0. You can't pause it at zero...

> Which is not to call apple's timer nonsensical.

It pretty much is, since the last 'second' takes more than a second to elapse.

It's not a "handling of time" its just a display. And its extremely sensible to round to the nearest displayable number instead of rounding up or down, because this minimizes the error in the displayed number. And that's what you are interested in, conveying as accurately as possible what the current time is.

You can

   - Round (Truncation is a type of rounding, Rounding towards zero)
   - Adjust the display to increase the precision it displays
   - Do both by dynamically increasing the precision of the display/decreasing rounding as the distance to zero closes in.

Isn't that exactly what you did right here?

Rounding is something I learned in elementary school. If someone in elementary school was unfamiliar with rounding, it would be mean to take them to task about it. But this writer is an adult, a professional programmer, and presumes to be a teacher, by taking the time to publish an article about the subject.

In fact, the writer has even less excuse, because he knows about rounding. Twice he mentions "rounding down". So it is all the more baffling that he did not call what Apple was doing, simply, "rounding up". Instead he wrote a multi-paragraph blog post about adding 500 milliseconds of "fake time", then having to duct-tape over that by making the timer say "0" when the timer reached 500 ms.

Suppose a man bills himself as a car salesman, but every question you ask him about the car, he says the wrong thing. He says the car has 3 wheels when it has 4. He says it is red when it is black. He says the engine is in the back when it is in the front. Would it be mean for you to mention his title, by saying something like, "You say you are a car salesman, but you don't know about this car on your lot." It is right to call someone out for being less than what they say they are.

As for random blog posts on the internet, this isn't so surprising. What's surprising is that it wound up on Hacker News with over 100 votes.

"What time is it now?"

vs

"How much time is left?"