Within the /system/expressionengine/third_party/ directory, copy the date_field_filter folder into your sites ./system/expressionengine/third_party/ directory.
Go to the Extensions area in the ExpressionEngine control panel, find Date Field Filter in the list, and click Enable.
Setup and configuring:
Use of this extension requires that an additional extension hook be added to the mod.channel.php file of your EE install. Consult the documentation on this for more information.
Within your sites ./system/expressionengine/third_party/ directory, delete the date_field_filter folder and upload the new one from the /system/expressionengine/third_party/ directory in your download package.
The extension will update automatically, and requires no further action from you.