11:30 in Engpsh is written as "eleven thirty" or "half past eleven".
The origin of this method of telpng time comes from the ancient Romans, who divided the day into two 12-hour periods: the first period ran from midnight to midday (ante meridiem, or AM) and the second period ran from midday to midnight (post meridiem, or PM).
For example:
"I'll meet you at eleven thirty." (我会在11点半和你见面。)
"The store closes at half past eleven." (商店在11点半关门。)