Unlike course periods in fixed marking periods, grade posting period for custom date-ranged course period differs in openSIS. Since custom duration is a user choice and it may vary with each course period, openSIS automatically considers a generic grade posting period for such courses, i.e.
Grade posting begins date = 5 days prior to custom duration's end date, and
Grade posting ends date = School's full year end date.
A course period that is created for a duration of 20 days in the month of Septemper, say sept 1st - sept 20th, and the school's fully year is set from January 1st - December 31st. The teacher assigned to this course period will be able to input final grades for students from Sept 15th till Dec 31st.