Dec 22 was celebrated as the Pagan Festival Of Winter Solstice and June 21 was celebrated as the Festival of Summer Solstice. ( Solstice derives from Sol ( Sun ) and sistere ( to stand). The Sun seems to stand still as he reaches his maximum declination of 23 deg 27 minutes positive on Jun 21 and 23 deg 27 minutes negative on Dec 22 ! )). On Jun 21, the Sun begins his southerly movement in the Tropical Zodiac, Sayana Dakshinayan and on Dec 22, exactly 180 degrees opposite, his northern movement, Sayana Uttarayan.
After moving 3 more degrees or 3 days, the Sun gets resurrected, so to say, on Dec 25th ! After 3 days He, the Sol Invictus, the Invincible Sun, is resurrected !
UN declared June 21st as the International Day of Yoga, adopting an Indian-led resolution and recognising that "Yoga provides a holistic approach to health and well being". This was adopted on Thor's Day or Thursday, the Day of the Guru !
While Bhauma Guruthvakarshan, terrestrial gravity, keeps us rooted to the ground, it is Khagoleeya Guruthvakarshan, celestial gravity, which makes the planets revolve. The word Guru is derived from Guruthvakarshan ! Hence Sun becomes the Guru here and his passage through the 12 Zodiacal Signs, the Dwadasa Rasyatmaka Jagath, symbolises the Guru with the 12 disciples. This is the symbolism of the Ashram, with the Guru as the Central Spiritual Sun, around whom the disciples revolve.