FilePattern with year as date shows year+1

<RollingRandomAccessFile name="File" fileName="${filename}"
        filePattern="logs/icap.log-%d{yy}.%i">
      <PatternLayout pattern="%m%n"/>
      <Policies>
        <OnStartupTriggeringPolicy />
        <TimeBasedTriggeringPolicy interval="12" modulate="true"/>
      </Policies>
    </RollingRandomAccessFile>