This add-on implements seasons to Minecraft. After a set amount of time there will be a seasonal change and this is most visible by the leaves shifting colors. It's very realistic in that sense that it is a gradual shift which happens quite slowly over a longer time. All leaves except for jungle leaves change colors, but that is going to be updated in a future release.
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Changelog
-Removed adfly links. Now the addon can be downloaded directly from Mediafire