Once upon a time, FA updated the banner monthly and it usually changed with the seasons of the northern hemisphere. In ye olde times, it only made sense for the banner to change with the weather, as it was the most significant and universal event to capture (even though it was still irrelevant to the southern hemisphere but yknow, they're a minority so whatever).
....however, in the days of today where it changes two, maybe three times a year, they could probably ditch basing it off of seasons. Like jeez, either be lazy about it and make it irrelevant to monthly changes or make it monthly again. Not thaaaaat hard. I'd be okay with banners few and far between if it was't like... autumn themed in the middle of winter, just as one example. :P
Nah forget it, they were just too lazy
....however, in the days of today where it changes two, maybe three times a year, they could probably ditch basing it off of seasons. Like jeez, either be lazy about it and make it irrelevant to monthly changes or make it monthly again. Not thaaaaat hard. I'd be okay with banners few and far between if it was't like... autumn themed in the middle of winter, just as one example. :P
...about 9/11. :^)