This was also explained by a dev once (Fernehawles, maybe? I can't seem to find the post) that for the purpose of overall storytelling, units of time such as years don't even follow the in-game time perfectly and are better tied to the completion of main story quests. Depending on when someone joins the game and completes the quest, you could have claims that some major battle (or maybe a moon falling??) happened in the year 1572 or say 1584 according to the in-game clock. Clearly such events only happen once and the devs need to ascribe a defined time to that. Essentially, time is frozen between quests. That and I doubt our characters are living to be hundreds of years old with no signs of aging. Realistic time is just something that needs to be given up in the concept of most games.