This is an interesting year. This year Pradosha puja and the winter solstice happen on the same day (well, where I live anyway. In the northern hemisphere), making it quite an auspicious time and a pretty good day to spend in prayer, meditation and for making new resolutions -- or rather, for stating your intentions for personal growth for the coming year. Also, for those who have an affinity for either Jyotish (Vedic astrology) or the science of astronomy, this day comprises a 21 hour window during which time there is a direct line between Earth and the Galactic Centre, the rotational centre of our Milky Way galaxy.
The seasonal significance of the winter solstice is that our days will now get longer and longer. It is the reversal of the gradual lengthening of nights and shortening of days. Depending on the shift of the calendar, the winter solstice usually occurs on December 21-23 each year in the northern hemisphere and June 20-23 in the southern hemisphere. Cultures and faiths around the world interpret this event differently, but most northern hemisphere cultures use the day to celebrate renewal and rebirth, and to hold festivals and gatherings, perform rituals, or enjoy other celebrations. In England the Druids, the native pagan culture, are celebrating at the Stonehenge national monument.
Pradosha commemorates the story of Shiva drinking the poison Halāhala, that was churned up from the eternal ocean, and saving the world -- earning him the epithet Nīlakaṇṭha, the Lord with the blue throat. It falls on the 13th lunar day during the waxing and waning phase of moon in the Hindu lunar calendar, occurring between 4.30 pm to 6.00 pm in England. The Pradosha time is a good time to do puja and pray to Lord Shiva and invoke his blessings. It is believed that worshipping Lord Shiva at Pradosha day will relieve sins and lead one to spiritual liberation.
And if you believe that the Divine exists in all creation, from the infinitesimally small to the unfathomably large, from the place inside our hearts to the very heart of the physical Universe, then knowing that today, for one of the few times during the Kali Yuga, a direct line is open between the Earth and the centre of our galaxy -- just might invigorate your mind and emotions and empower your devotions.