Long and short of it
The winter solstice, also known as the end of winter, falls on December 22 in the Chinese calendar. In the northern hemisphere, it is the shortest day of the year, with daylight (yang energy) at its minimum and night (yin energy) at its maximum. Hence, it is considered the coldest day of the year. More importantly, it marks the transition between winter and spring, because it indicates warm weather is about to arrive.
In ancient China, the festival was a major event, as it meant farmers could start spring cultivation. In the imperial era, the emperor would lead the annual sacrifices at the Temple of Heaven in Beijing, a procession that foreigners and most Chinese were forbidden to witness. In modern Hong Kong, a significant number of companies still give their employees the afternoon off for the occasion.
Most Hong Kong families mark this night by reuniting for a feast, which will include glutinous rice dumplings served towards the end of the meal. Offerings are made to ancestors and family members who travel a lot return home as a sign of respect to their forebears and to show they have reached their destination for the year. The winter solstice is also seen as a time when everyone is essentially a year older, even though the year is not officially over.