When are you going? Unless it's some really peak day (e.g., Christmas) and/or you wanted a very specific time and/or you have a really large party, dining reservations at DLR are generally much easier to come by. I'm not saying you shouldn't make a reservation, but DLR is nothing like WDW when it comes to making dining reservations...it's much easier. So I wouldn't worry about trying to figure out when the system rolls. Just note that if you try to make a reservation on the 60-day mark and it shows nothing is available, it's more likely that they haven't yet loaded them into the system (instead of being already fully booked).