Here is the same data as defined by another airline
Please note the dates for a change in fare based on travel loads can vary from a day or two to more than a week depending on what day of the week the first or last day of a month falls or other special events. Therefore, use this chart as a "general" guide and ask your travel agent for the specific dates when you plan to travel.
Those traveling on missionary rates on British Airways between December 25 and June 30 and between August 16 and December 12 can expect the best airfare rates. Those traveling between July 1 and August 15 and December 13 through 24 will have higher rates.
If you travel in the peak period of June, July, and August, you need to make your reservations as early as possible as these seats fill up fast. British Airways does not charge to book reservations several months in advance through a travel agent, but about 30 days before travel you must purchase the ticket or lose the reservation. I try to have all our team members names in their reservation system by 15 February but was able to add a team member in late April one year for a early July trip.
I assume similar travel dates apply through other gateway cities. Also, some travel experts suggest the optimum time to purchase tickets is 76 days before travel. The reality is the airlines have spent major bucks on powerful computers and programs that change rates continually in response to the number of searches, special events, even local news for a given destination.