Character mistake: Tai says "And it started to snow in the middle of July" but later you find out that it takes place on August first.
Character mistake: Agumon says that they were away from the digital world for a couple of days. But in the previous episode Tai and Agumon were back on earth for only a few hours.
Now Apocalymon - Part 1 - S1-E53
Character mistake: Gabumon says that all of the Digimon are at their rookie level, but Gatomon is not a rookie level Digimon, she is a champion level Digimon.
Answer: We are never told as to how they got there.