It is useless to measure the oxygen production every hour for 24 hours because oxygen is produced during day time due to the presence of photosynthesis process. Oxygen is produced in large amount during photosynthesis, some oxygen is used in respiration while the remaining diffuse out from plant body through stomata. After vanishing sunlight, the photosynthesis process stop and no production of oxygen occur. So only measure oxygen production at daytime as compared to every hour for 24 hours.
Complete orbit around the Sun takes about 365.26 days. The Earth’s rotation axis is tilted relative to the imaginary space orbit around the Sun.  This imaginary plane is called the ecliptic plane.  Position of northern and southern hemisphere toward the Sun varies depending on the season
