What is Excise Return Dates for SSI(small Scale ind)

Hi, As per rule 8 of central excise rules 2002 & as per  Rule 9 (8) of CENVAT CREDIT RULES 2004, SSI have to pay monthly excise duty before 15 days from the end of the month, at normal mode.... or before 16 days in case of electrionic mode...... they also have to file quaterly  return before 20 days from the end of such qtr........