This is in fact pretty confusing as Sydney, Tokio, London and New York have different daylight savings schedules.
Sydney: DST from Oct 5, 2014 to Sun, Apr 5 2015
Tokyo: No DST
London: DST from Mar 29, 2015 to Oct 25, 2015
New York: DST from Mar 8, 2015 to November 1, 2015
This means that right now Sidney still has DST, while New York already has DST, whereas London will start DST in two weeks, while Tokyo does not participate in that game.
I think that it is more or less impossible to follow all those different time zones and changes, and therefore I focus on the New York close at 5:00 PM EST. Logically that close ends the trading day that started in the Far East then continued with the Tokyo/London overlap and the London/New York overlap. New York and Tokyo do not overlap, there is a hole of 1 hour in winter and 2 hours in summer between the New York close and the Tokyo open.
For trading strategies, I basically use 5:00 PM EST as the start of the new trading day, which currently falls together with the Sidney open (this will change in April when Sydney switches back to standard time). Alternatively the Tokyo open at 6:00 PM EST (in winter) / 7:00 PM EST (in summer) could be used.
The Tokyo open does not have a meaning to me. If something happens over the week-end the price will already gap up or down when the Sydney session starts. Therefore the Tokyo open comes late. An evaluation of volume - particularly on Sunday evening / Monday morning suggests that the correct session to select is 5:00 PM EST to 5:00 PM EST. And this is also the simplest solution.
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