dao man - 2010-09-04

Hi !
after I spent a week to research the Attendance screen, I still don't know what cellid2 in the file new_week.ftl (//specialpurpose/mypage/webapp/mypage/calendar/new_week.ftl) for?

here are the code:

<#list periods as period>
<#assign cellidt1=period.start?date>
            <#assign cellid2=cellidt1?substring(4,6)>
     <#if cellid2?ends_with(",")>
            <#assign cellid2=cellidt1?substring(4,5)> 
   
  <#assign cellid = (cellid2?number % 7)>
<#assign cellid = 0>
    <#if cellid=0>
<#assign cellid=7>
</#if>

this code made error because if cellidt1 = 30-Aug-2010 then cellid2=ug => (cellid2?number % 7)--->error

What purpose of cellid2 ?
Why cellid2?number % 7 ?

Thank you for your help !