Harvey the hacker hacked my clock. At first, the results made no sense, but I eventually figured out his logic.

At 12:00, the clock shows 12:19
At 12:01, the clock shows 12:15
At 12:02, the clock shows 12:18
At 12:03, the clock shows 12:18
At 12:04, the clock shows 12:17
At 12:05, the clock shows 12:18
At 12:06, the clock shows 12:19
At 12:07, the clock shows 12:16
At 12:08, the clock shows 12:20

At 12:09, what will the clock show, and why?


At 12:09 the clock should display

12:19, as the minutes count the 19 lit segments of 12:09 in seven-segment display.

The start 12:0 has 13 segments, then 0>6, 1>2, 2>5, 3>5, 4>4, 5>5, 6>6, 7>3, 8>7, 9>6.

enter image description here

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    $\begingroup$ The image shows a differently counting (hexadecimal) device though. $\endgroup$ – Bass Jul 20 '19 at 20:51

If your unhacked clock displayed 9 like this

5 seg 9
then at 12:09 your hacked clock will show 12:18.

If your unhacked clock displayed 9 like this

6 seg 9
then at 12:09 your hacked clock will show 12:19.

The minutes have been hacked to display the count of lit segments in the unhacked time.

This should be a comment on Tom's answer but I can't put spoiler tags or images in a comment.

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    $\begingroup$ (This adds one very minor detail to the accepted answer. As a general suggestion: if you're posting an answer that's largely the same as an existing one, acknowledge the prior answer and indicate how yours differs, improves upon, or adds relevant detail to the answer already provided. That way there's no confusion about whether or not you just didn't see the earlier answer. And, of course, if you can't really explain why your answer is not in essence a simple duplicate, that's probably a good sign that your answer isn't adding anything to what's already been said, and shouldn't be posted.) $\endgroup$ – Rubio Jul 21 '19 at 11:17
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    $\begingroup$ To answer your question, ROT13. $\endgroup$ – wizzwizz4 Jul 21 '19 at 17:15

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