Tea time in a house with children is less a meal than a schedule, with everything before it timed to land in the right order. If 5:12 pm is when it needs to be on the table, the countdown here is more use than an estimate, updating continuously as the afternoon runs down.
When the clock reaches 5:12 pm, the count does not sit at zero. It rolls straight over and begins again towards the same time tomorrow, on its own, without a refresh or a reset. That makes this a page worth keeping in a bookmarks bar rather than one you look at once and forget.
British speech has a well-worn habit of dropping the middle out of a time: half seven means half an hour after seven, never half an hour before it. Quarter past and quarter to work the same way. Written down, the same moment appears plainly as 5:12 pm, or as 17:12 where no ambiguity is allowed.
Common questions
What is 17:12 in the 12-hour clock?
That is 5:12 pm, or twelve minutes past five in the evening if you are saying it aloud. From 13:00 onwards, subtracting twelve gives the pm figure — the same moment written three different ways.
Does the number update by itself?
Yes. It recalculates every second from your device's clock, so there is nothing to refresh or restart. Whatever is on screen is the current gap to the target time, not a figure worked out when the page first loaded.
What happens if 5:12 pm has already gone for today?
The count simply carries on towards the next occurrence, which is tomorrow. That rollover happens on its own — the page does not need reloading and there is nothing to reset by hand.
Which clock does it use?
Your own. It reads the local time and time zone from the device you are looking at, so the figure reflects where you actually are rather than a fixed zone written into the page.