Да: установите для элемента datePattern
значение "yyyyMMdd-HH"
<appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
<file value="logfile" />
<appendToFile value="true" />
<rollingStyle value="Date" />
<datePattern value="yyyyMMdd-HH" />
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
</layout>
</appender>
Ref: log4net Примеры конфигурации .