Trains home fill up in a fairly predictable order, and being on the platform a few minutes earlier changes the journey considerably. This page tracks the exact time left until 4:50 pm, whether that is the train itself, the walk to the station, or the point work has to stop for either to happen.
The figure on this page comes from your own device's clock, checked continuously and recalculated every second against 4:50 pm. There is nothing to press and nothing to set up first — the count is already running by the time the page has finished loading, and it keeps going while you are looking at it.
Twelve o'clock is where the 12-hour clock is at its weakest, since 12 am and 12 pm are read the wrong way round often enough to cause real trouble. Writing a time as 16:50 removes the problem outright, because a 24-hour figure only ever points at one moment in the day.
Common questions
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 4:50 pm, 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.
What is 16:50 in the 12-hour clock?
That is 4:50 pm, or ten to 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.