Be aware that the changes are much different when using the AdoNetAppender. In that case, you need to change the parameter settings:
<parameter>
<parameterName value="@log_date" />
<dbType value="DateTime" />
<layout type="log4net.Layout.RawUtcTimeStampLayout" />
<!--<layout type="log4net.Layout.RawTimeStampLayout" />-->
</parameter>
This change will now write the correct UTC value for the logDate field.