On- used when a following noun refers to an organized presentation of a subject -- a detailed, somewhat formal and thorough treatment of a subject
a lecture on nutrition and diet
a tape on pronunciation
About- more informal
information about caring for a sick child
a brochure about travel in france
On time- ON time, very specific (much more formal)
About time- about time,close to time
a lecture on nutrition and diet
a tape on pronunciation
About- more informal
information about caring for a sick child
a brochure about travel in france
On time- ON time, very specific (much more formal)
About time- about time,close to time