A tropical phenomenon, twice a year
Zero Shadow Day
Hari Tanpa Bayangan
There is a day when the sun stands directly over your head. At midday your shadow disappears beneath your feet. It happens everywhere in Indonesia — and almost nobody knows. Find the date for your own city below.
A personal educational project. Not an official product of any institution. Method
Why does it happen?
The sun drifts through the year
The point on Earth directly beneath the sun does not stay put. It travels north until June, then back south until December.
Twice, it passes your town
Indonesia lies between those two limits, so that point crosses every city in the country twice a year — once going north, once coming back.
That day, the shadow goes
With the sun straight overhead, a vertical object has no shadow in any direction. It lasts a couple of minutes, and then the shadow returns.
Place
6.2088° S · 106.8456° E · UTC+7
Coordinates never leave your device. No network request, no reverse geocoding, no analytics.
Try it yourself
- ShadowTurn the view, drag the time, and watch the shadow shorten until it is gone.
- DatesYour two dates, the time of culmination, and why it is not 12:00.
- CurvesThe trace of the shadow’s tip through a day, and the figure-eight the sun draws.
- EratosthenesMeasure the circumference of the Earth with two sticks and a ruler.
- SweepWatch the sun’s band sweep across the archipelago through the year.
The latitude directly beneath the sun sweeps between 23.44°N and 23.44°S over the year. Indonesia lies entirely inside that band, from Sabang at 5.9°N to Rote at 11°S. So every place in the country gets two zero shadow days: once as the sweep heads north, once as it returns. Nowhere in Europe, North America, or most of China ever gets one.
Shadows point north for part of the year and south for the rest. Outside the tropics they only ever point one way.
Solar noon is not 12:00. WIB is anchored to 105°E while Banda Aceh sits near 95°E — nearly ten degrees west, so its solar noon runs roughly forty minutes later than the clock implies.