Just like in any language, the task of telling time in English has its features.
In the USA and the UK a 12-hour system is used. We do not say 13:00 hours there, we say 1:00 PM; we do not say 15:00 hours, we say 3:00 PM, etc.
Below you can find ESL hours worksheets and a lesson plan for teachers. They will help you to understand time in English better.