Overview
- The moment arrives on Dec. 21 at 9:03 a.m. CST (10:03 a.m. EST), when the Sun sits directly over the Tropic of Capricorn.
- It is the year’s shortest day, yet many locations saw their earliest sunset in early to mid‑December, including Boston around Dec. 8 and varying UK dates by latitude.
- The offset between earliest sunset and the solstice results from Earth’s axial tilt and slightly elliptical orbit, which cause “sun time” to diverge from clock time.
- After the solstice, daylight increases slowly; Chicago has just under 9 hours 11 minutes on Dec. 21 and reaches a 4:31 p.m. sunset by Dec. 31.
- Day length depends on location, with London near 7 hours 49 minutes 42 seconds on Dec. 21 and far‑north sites like Lerwick seeing earlier sunsets.