The 24 hour clock is still not universally adopted in the UK. No English speaker says says "thirteen O'Clock" the way one might say "treize heures". English sp

The 24 hour clock is still not universally adopted in the UK. No English speaker says says "thirteen O'Clock" the way one might say "treize heures". English speakers might say "thirteen hundred hours", but only in restricted circumstances (e.g. in the military).