Yep, can you please write this up on github as an issue?
I experienced the same issue until I performed the magical “refresh browser cache”. After that all times were in 24 hour format 
Even for input_datetime details? I tried refreshing, and even another browser.
I will check tomorrow if anyone have reported it as an issue, and I will do it if not.
Please fix this bug. I have never ever had any problems getting a system/app/os/programming l to let me choose the time format i want.
I live in Sweden, If i set swedish as language in HA i get 24h clock. But i want to use english but then i get am/pm time format. Is it possible to use English language and get 24h clock? Thx…
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Set it to English (GB).
For more information, see this post:
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Like mentioned a couple of times, set your language to English (GB) instead of English for the 24h time format.
There must be something wrong, as in my case it doesn’t work.
Ok, so I tried “solution” with English (GB). I have got what I want (24h format).
I’ve read the thread until the end and honestly I was not able to switch Chrome to display dates in logbook in 24H format.
Chrome sends the following in request header:
Accept-Language: en-GB,en;q=0.9,nl;q=0.8
I cannot remove “en” from that list because this is default Chrome language.
In console (opened for HASS website) I get the following:
> window.navigator.language
"en-GB"
> new Intl.DateTimeFormat().resolvedOptions().locale
"en-US"
> new Date().toLocaleTimeString()
"11:15:20 PM"
The only where “en-US” can leak from is that it is a Windows System language (used for Windows interface). The user’s region is set to UK.
The same difficulty with Home Assitant app for Android which does not display history in 24H format. In App Settings one can find the language settings with two choices: “Device Language” and “English (en)”. My device language is “English (United Kingdom)”.
I will appreciate if one succeeded with any above.
P.S. I cannot test Firefox, because Home Assistant UI simply does not work (files with message can’t establish a connection to the server at wss://hass.website/api/websocket in console however network log is error free, probably that is issue 8318).
Let’s upvote this feature request…
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There’s a PR open to enable this:
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And it’s merged into dev, which means it would typically be part of the next release!
Thanks @spacegaier and @Bram_Kragten for your work on this!
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Sorry, can’t seem to find where this is fixed 
How do I enable 24 hour format ?
Click on the PR link above for a screenshot.
Thanks alot Koying!
Was looking under det Person´s… But good its a general setting.
I recently changed to 24h clock, but noticed by a pure coincidence that the system incorrectly represented 00:50:29 as 24:50:29 in the plot of one of my sensors.
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state after 2021.10:
Firefox: 24 and UTC
Chrome: am/pm and localtime
I want 24 and localtime.
Change your time format under your user. This setting needs to be applied on your user per browser.
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