SeasonI

In 2003, Orcs and Minax behind them were intriguing ageinst the realm. Royal Britannian Guard was organized.
Along the official scenario, almost the same shape/color/name items released on almost all western shards equally.
So it's official, It's easier to get information about the events from BNN than shard specific EM events.
*edit: articles before Jan. 2004 are not available from search form at this moment. But you can still access the source by changing the article number in web address.*
I think the period of Season I is roughly from June 2003 to the end of the year or early 2004.
As for the start, revenger Lord Blacktohrn was defeated in 30th June 2003, when his cursed weapon Treachery was lootable off the courpse on each shard.
For the end, it's just before a gap before April event, in other word, the start of the Season II.
I can say, a little more strict start of Season I is an article "Travel Advisory Alert!" published in BNN 8th September.
It's a beggining of the following The King's Return and Departure plotline.
At that time, it seems EM was more a apprentice helper on the official plotline than an real Event Moderator with his own individual plot and schedule.
And while Treachery is listed in Season I, it's more unlike EM rare. Granted it's property is vary by shard(see Treachery, Season I), It was available on non EM shards at least all Japanese shards.
As you maybe read in Introduction, Japanese shards almost never had Event item from 2000. I don't know why, but anyway it's indeed something strange not only for EM shards but also non EM shards.