Twice a year, the various friendly herds meet up with each other as they pass north or south with the seasons.
In this world, the Mane 6 have been friends for quite a while. They might not be AS close as they are in canon work but they are as best of friends as non-herd mates can get. It’s also usually a prime time to meet other ponies for potential spouses, though for the most part, these six haven’t really bothered with all that.