The last train back is the one time in an evening that genuinely will not wait, and working backwards from it is how people end up leaving earlier than they meant to. If 7:24 pm is that departure, the countdown here gives the exact figure rather than a comfortable guess.
The count makes no sound and asks for no attention while it runs. It is a number, not an alarm, and nothing goes off when it reaches zero. Leaving the page open in a background tab is perfectly fine — it will carry on counting towards 7:24 pm whether or not anyone is watching it.
Plenty of phones, laptops and dashboards default to a 24-hour display regardless of how people around here actually talk, so 19:24 may well be the figure staring back at you even though 7:24 pm is how the same moment would be said aloud. Neither is more correct than the other.
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 7:24 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 19:24 in the 12-hour clock?
That is 7:24 pm, or twenty-four minutes past seven 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.