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