1. Дни недели, конкретные даты (on the next day, on the 1st of January, on my birthday). 2. Местонахождение (on the table, on the ground, on page 6, on the left). 3. Кода говорим о способе передачи информации (on air, on the news, on tv, on the radio). 4. on holiday, on vacation.