5. Explain what must happen to our calendar if Earth revolves around the
Sun about every 365 days.

Every 365 1/4 days (not exactly 365 days), the Earth returns to the same exact spot in its orbit. That is why we have a leap year roughly every 4 years, to synchronize the seasons with our calendar; if we had a 365-day calendar every year, the seasons would drift around the calendar.