Length of Days

The first graph shows how the number of hours from sunrise to sunset change on different locations. Data for two years is shown.

The graphs are generated using the wonderful flot javascript graphing library. If the page is slow and you are using Internet Explorer I can't help you. If it is very slow in other browsers please let me know.

The second graph shows how much the the day-length changes, in hours, each day. (The first derivative of the above.)

Select which locations to show:

(Tip: Turn off all except Quito to see how little variation in day length there is at the equator)

Show custom location

You can add graph for a custom location by providing a latitude/longitude coordinate set below. You could use touch map to find the coordinates.

Set date range

Comments

On August 20th 2009 at 10:08 Eridal wrote:

It will be very useful if I can set my own location.

can you provide an easy way to do it?

On August 21st 2009 at 1:54 Jacob Oettinger wrote:

Good idea. I have added the option to provide a custom location that will be added to the graphs.

On August 28th 2009 at 10:11 davesnout wrote:

I've been looking for a site where these graphs are plotted for ages. Found you at last. Thanks for putting this up.

On July 31st 2010 at 22:46 wrote:

On January 3rd 2011 at 7:49 Jane Heritage wrote:

Oh dear, I can't make the "enter your own location" feature work - I get an error 404. What a shame!

On January 3rd 2011 at 8:00 Jacob Oettinger wrote:

Hi Jane

I have fixed the error, so it should work now.

On January 19th 2011 at 6:56 Ben wrote:

Custom Date Range?

On February 10th 2011 at 3:17 Jacob Oettinger wrote:

Quick and dirty Custom Date Range added.

On March 12th 2011 at 6:09 User wrote:

I also get an error 404.

On March 12th 2011 at 7:08 Jacob Oettinger wrote:

Fixed.

On April 20th 2011 at 6:19 wrote:

On June 20th 2011 at 23:16 Jonathan wrote:

in what form do you enter the coordinates to make the custom thingy work?

On June 21st 2011 at 1:24 Jacob Oettinger wrote:

They should be entered in decimal form. Copanhagen is:

Latitude: 55.693403
Longitude: 12.583046

On September 22nd 2011 at 9:08 Dan wrote:

Excellent tool, thank you very much. The day-length change graph shows some strange blips in early March and early November (turn off Norway and Antarctica to see it better). Why is that?

On September 22nd 2011 at 13:53 Jacob Oettinger wrote:

I expect it is an artifact of the fact that the graphs are not continuos, they are made out of many very small linear pieces. But I am not sure.

I just looked a bit more at it now. A real continuos graph (except for areas with constant night or day) could be created from the formula that can be found here: http://en.wikipedia.org/wiki/Day_length

Wikipedia ftw!

On September 23rd 2011 at 10:09 Dempsey wrote:

The change in the length of day is fractions of hours per day. To calculate the actual number of seconds change for one day you need to multiply the value on the graph by 3600 and then multiply by 24 hours.

On March 11th 2013 at 18:09 Rick wrote:

Is not theY axis on the second graph days instead of hours? That would make more sense.

On March 11th 2013 at 23:35 Jacob Oettinger wrote:

@Rick. You are right. I have updated the calcualtion so that the change is in hours now.

Thanks.

Comment ?

Add a new comment. (javascript required)

Name		(required)
Email		(will not be published)
Website
Comment