Don't lose any sleep over it.

"Global warming likely will shorten the length of the day by about 120 millionths of a second during the next 200 years, according to scientists Felix Landerer, Johann Jungclaus, and Jochem Marotzke from the Max Planck Institute for Meteorology in Hamburg. "
http://news.com.com/8301-10784_3-9725495-7.html?part=rss&subj=news&tag=2547-1_3-0-5