Find the time
The time has a format: hours:minutes. Both hours and minutes has two digits, like 09:00.
Make a regexp to find time in the string: Breakfast at 09:00 in the room 123:456.
P.S. In this task there’s no need to check time correctness yet, so 25:99 can also be a valid result.
P.P.S. The regexp shouldn’t match 123:456.
The answer: \b\d\d:\d\d\b.
alert( "Breakfast at 09:00 in the room 123:456.".match( /\b\d\d:\d\d\b/ ) ); // 09:00