well, lets look at this in a linear manner.warning, im about to go deep into analysis, so be ready. assuming the seasons work the same for them they do for us, things get complicated. the start of the series is summer, thats a constant. ok, first seasons a lead up to the ggg (grand galloping gala). now, if we look into events in "sweet and elite," twilight says the galas coming up. either a sceond year had begun, the galas more than once a year, or i dont know what the bucks going on.
then theres hearths warming eve, obviously comes during winter. safe to assume it comes between fall weather friends and winter wrap up, if were assuming it really has only been one year.
then theres pinkies birthday. party of one pretty self explanatory. then in a friend in deed she says her birthdays mot for 70 something days. either its been a year since party of one, or friend in deed takes place before that, or we have some real continuity issues.
then theres the recent episode, "tanks for the memories". *spoiler* (but i doubt anyone here hasnt seen it yet) we learn that it was to be their first winter since meeting. now, she first gets tank back in season 2. but then raises a few questions. if this is the case, then the earliest she couldve gotten him was spring, not long before season 4 premiere. meaning, the 2 of them hadnt been together as long we were led to think. which makes her little rampage make even less sense.
my overall analysis: the timelines completely bucked, or someone wasnt paying much attention.