First trains, night buses and the early crossings all leave before most alarms have gone off, and a few minutes either way decides whether you make one. This page counts down to 12:40 am exactly, which is more use than glancing at a phone and rounding the answer to the nearest ten minutes.
Rather than rounding to the nearest minute, the count tracks hours, minutes and seconds the whole way down, in one line. That precision matters most in the last stretch, when the minutes turn into single figures and the difference between leaving now and leaving shortly stops being academic and starts costing you the train.
Said out loud, 12:40 am usually comes out as twenty to one at night rather than as a string of digits. Spoken and written time diverge more than people expect, which is worth remembering when somebody tells you a time over the phone and you are trying to match it against something printed.
Common questions
What is 00:40 in the 12-hour clock?
That is 12:40 am, or twenty to one at night 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 12:40 am 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.