Greg Hewgill (ghewgill) wrote,
Greg Hewgill

sunrise and sunset

Daylight Saving time just ended today in New Zealand. At this latitude (43°S, about as far south as Portland is north), the the axial tilt of the earth has more effect on the sunrise and sunset times than where I've been living recently (35°N in California and 30°N in Texas). The variation is also important for me these days since I'm now cycling to and from work year round.

In order to visualise the sunrise and sunset times over the course of a year, I used data from the USNO Sun or Moon Rise/Set Table for One Year service and the Google Chart API to create a sunrise/sunset graph with a correction for daylight saving time (click for a larger version):

This visualisation neatly shows that daylight saving time tries to keep sunrise within about a two hour window (6am to 8am) while sunset is allowed to vary over four hours (5pm to 9pm) during the course of a year.

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