The first half of Konosuba episode 4 shows a montage of Kazuma and Megumin training, leading us to believe it went on for a long time. Long enough for the seasons to change several times.
It seems to me that it wouldn't take too many for the event that happens halfway through the episode to happen, so I don't think it was a year like was implied with the changing of the seasons during the montage.
How many days has it been?