Board Thread:The Reference Desk/@comment-60605-20140919101627/@comment-1827503-20140919165714

The crossovers with Doctor Who and Torchwood make a general time period easy to find. The Stolen Earth/Journey's End takes place no earlier than March 2009 and no later than September 2009, as this is the only time period where Torchwood Three consists of Jack, Gwen, and Ianto. As the two-parter is known to be in the SJA Series 1–2 gap, this narrows it down significantly. However, I found more concrete proof:


 * As of Invasion of the Bane, K9 Mark IV has been in deep space for eighteen months, placing it no earlier than mid-July 2008, and likely in around late August or early September.
 * In Turn Left, Clyde is already part of Sarah Jane's gang by the time of the Royal Hope Hospital incident (Smith and Jones). This would appear to place SJA Series 1 in early 2008, but as Turn Left occurs in Donna's World, it's possible that the Trickster manipulated events to place it earlier than in the main timeline.
 * Revenge of the Slitheen takes place shortly after after Invasion of the Bane, so the Park Vale school year appears to start in early September. From this point onwards, we can generally assume the rest of Series 1 follows RTD's general policy of being a year ahead of real life. This continues through the end of Series 4. (The Nightmare Man has Luke going to university a year early, so SJA Series 4 remained a year ahead despite Doctor Who reverting to the present day. This places Death of the Doctor in autumn 2011, around six months after the Lake Silencio incident.)
 * Sky appears to mark the point where SJA switched to present day. Sadly, with Lis Sladen's death, it's impossible to prove. Any dates on SJA Series 5 stories are purely speculation.