Try this (It should be OK!):
<appender name="LogFileAppender" type="log4net.Appender.RollingFileAppender">
<file value="logs\\" />
<appendToFile value="true" />
<DatePattern value="yyyy\\\\MM\\\\dd'.inf.log'" />
<rollingStyle value="Date" />
<param name="StaticLogFileName" value="false" />
<layout type="log4net.Layout.PatternLayout">
<header value="[Header] " />
<footer value="[Footer] " />
<conversionPattern value="%date [%thread] %-5level %logger [%ndc] <%property{auth}> - %message%newline" />
</layout>
</appender>
It will create a logfile named ‘logs\2010\04\02.inf.log’ (let date be 2010-04-02)