How many days before the journey date, 2S (second sitting) type railway tickets are available in the online IRCTC website?
The Indian railway tickets are available 120 days before the journey date in online and ticket counters.
Please refer the official announcement from the IRCTC website: Advance Reservation Period (ARP) for booking in trains is increased from 60 days to 120 days w.e.f 1st April, 2015.
I got the answer to my question.
If date of journey is more than 10 days then for second sitting it will show like this.
"Booking not allowed as the Date given is outside Advance Reservation Period"
For second sitting, the online booking is available 10 days before date of journey. Suppose DOJ is 13/01/2017 then they will be available from 03/01/2017. This is my observation only done on IRCTC site.