Tag for length of day difference from yesterday

Can we get a tag which will add the difference of length of day from yesterday. I believe we would have to seconds added to length of day there are times during the year when a day is 5 seconds longer or shorter then the day before. I am not sure if this can be done. I we cant get a tag added can we get the seconds added and i could always do a function in html and do it that way, but I would need seconds added to the length of day.


WD 10.35N