Far too many people have been having problems with this the past month, me included. Dynmap is a minecraft server mapping software run by many creative servers. It creates a birds eye view of the server to be seen in a webbrowser. It has a setting of creating a seperate night image where it switches after the server time. This is now broken and there is no official statements about it. And, as the newest version on the curse page is bugged and the 2nd newest is for 1.6.4(?) that is terrible. So: lets look at the fix.

Find it on bukkit. Yep. Bukkit has a more/less updated changelog.


http://dev.bukkit.org/bukkit-plugins/dynmap/
Look under the "Recent files" section on the right information bar. You will find 

• A: v2.1-alpha-1 for CB 1.7.9-R0.2Dec 03, 2014
  

(click the link if you want the easy way out)
which is the version that you want. It is supposed to be an alpha build, but this feauture was broken by the release. Download it and put it in your plugin folder instead of the original one. I can confirm this working with 1.8 even if it says 1.7.