User blog comment:TUSF/Light Novel Chronology/@comment-70.53.116.171-20170326163119/@comment-28251580-20170326211122

Spoiler alert in case you follow the link: First Day takes place before the events of Progressive. You basically have the introduction of the world with Kirito running from Klein in ep 1 of the anime / Volume 1 of the Light Novel. First day takes ironically place in the night that follows this event, whereas Progressive starts one month into the game. This story is referenced mildly in one of the later Progressive books.