It is the day on which the Earth's axis is tilted towards the Sun to the greatest degree (again, on the northern hemisphere).
(It; is; the day on which the Earth's axis is tilted towards the Sun to the greatest degree (again, on the northern hemisphere)) (the Earth's axis; is tilted; towards the Sun; T:the day)
It the Earth's axis
is is tilted
the day on which the Earth's axis is tilted towards the Sun to the greatest degree (again, on the northern hemisphere)
towards the Sun T:the day