Bakers, posties and lorry drivers halfway down a motorway are all at work while the rest of the country is asleep, and their day is measured against fixed times rather than daylight. If 12:05 am is a start, a stop or a delivery slot, the countdown here tracks it exactly and updates on its own.
Because the count reads straight from your device's clock, its accuracy rests on that clock being right, time zone included. Phones and computers normally handle this themselves, so in practice the figure here lines up with whatever time the device is already showing elsewhere on screen.
Plenty of phones, laptops and dashboards default to a 24-hour display regardless of how people around here actually talk, so 00:05 may well be the figure staring back at you even though 12:05 am is how the same moment would be said aloud. Neither is more correct than the other.
Common questions
What happens if 12:05 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.
Will this alert me when the time arrives?
No. It is a live number rather than an alarm — nothing rings, buzzes or notifies you at zero. If you need to be interrupted at 12:05 am, set an alarm as well and treat this page as the running total.
Is it affected by the clocks changing?
Only in the sense that your device is. When the change between GMT and BST happens at the end of March and October, the device adjusts and the countdown follows it without anything to do here.