Ok so first and foremost, HI and welcome to the forum.
2ndly please proceed with caution regarding the solution i'm about to give you as it is a "hack" It will not be supported, it will not persist after upgrades, and therefore you'll have to make the change after every upgrade, and you should make a backup of this file first, etc.
If you look at this file:
If you change the %I to %H as shown below... this will give you 24h (zero padded format... aka 01... 09, 10,11...24). You might have more requests around this... i suggest this site for reference: http://strftime.org/