The Dates given were outside ARP means that dates were outside Advanced Reservation Period (ARP). IRCTC these days gives an error Booking not allowed as the Date given is outside Advance Reservation Period
IRCTC allows you to book train ticket upto 2 months in advance but when I tried to book train tickets for 21 Sep 2013 on 22 July 2013, IRCTC gave the above error. I think calculation for each month in their system takes 30 days duration. Hence max 60 days ARP limit prevents from booking advanced ticket exactly before 2 months.
The error may also be because of July and August both being 31 days month (and perhaps will stay a day longer even in Dec-Jan month) Hopefully next day will land within ARP(Advanced Reservation Period) and "Booking not allowed as the Date given is outside Advance Reservation Period" error will not come.