for & loop tags optimization

calendar example 

<cml:use key='DESKTOP'>
<cml:for startparam='STARTDATE' endparam='FINISHDATE' delta='604800'
var='wdt'>
<tr>
<cml:loop counter='7' var='dt' delta='86400'>
   <td><cml:date expr='env(wdt)+env(dt)' format='%d.%m'/></td>
</cml:loop>
</tr>
</cml:for>
</cml:use>