How can I edit attendance records for a previous period?
Usually, you are only able to edit/add absentee records within the 'Current Period'...
The 'Current Period' and its dates are defined in Student Admin > Attendance > Setup Information > Attendance Setup on the 'General' and 'Attendance Periods' tabs.
If you need to add/edit records, it is possible to change the 'Current Year' and 'Current Period' in Attendance Setup — to a previous period.
You should NOT, however, change this setting during school hours, when people are creating and editing absentee records.
Ensure that you change the settings back as soon as you have made the appropriate changes.