XJO - Bear Posts only (Factors which might cause the markets to fall), page-23302

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Today the ASX markets opened a lot quicker than the usual staggered start. Has there been a change to this normal process?

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ChatGPT said:

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Yes, you’re absolutely right — today, June 23, 2025, marks a significant change in how ASX opens, and here’s what’s up:

Single-Price Opening Auction (No More Staggered Start)

• Old system: Since 1987, ASX had a staggered opening over about 10 minutes — tickers A–B opened around 10:00 am, C–F at ~10:02, then G–M, N–R, and finally S–Z around 10:09 am, each with ±15 seconds randomnessasxonline.com+8cpwealth.net.au+8rivkin.com.au+8.

• New system (SR15): Starting today — all cash equity stocks open simultaneously via a single-price auction.

  • Order entry starts at 7:00 am AEST.

  • At 9:59:00–9:59:15 am, a randomized Opening Single Price Auction (OSPA) occurs; this bursts all overlapping buy and sell orders.

  • Then comes a brief levelling/buffering period (~15–30 s).

  • Continuous trading begins precisely between 9:59:45 and 10:00:00 amen.wikipedia.org+8asx.com.au+8asxonline.com+8asxonline.com+2asxonline.com+2asx.com.au+2.

• Why? Technology improvements and international alignment mean the older stagger was no longer necessary. The change aims to:

  1. Minimise opening volatility,

  2. Boost liquidity, and

  3. Simplify infrastructure complexity**promotion blocked**.au+10asxonline.com+10asx.com.au+10.

New Post-Close Trading Session

ASX has also introduced a Post-Close Session alongside the traditional closing auction:

• Previously, trading ended at 4:00 pm, followed by a 4:10–4:11 pm Closing Single Price Auction (CSPA).

• Now, after that, there’s a post-close continuous session allowing further trades at the auction price — especially valuable for stocks releasing price-sensitive info near close**promotion blocked**.au+10asx.com.au+10hotcopper.com.au+10.

TL;DR — What Changed in One Chart

	Phase	Old (Pre-23 Jun)	New (From 23 Jun)
1	Opening	10 am–10:09 am staggered openings	7 am: pre-open; 9:59–9:59:15 am auction; ~10 am continuous
2	Closing	4 pm pre-close; 4:10–4:11 pm CSPA	+ post-close trading session after CSPA

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So yes — what you noticed is real. The ASX has switched to a synchronized, high-efficiency opening and enhanced the closing process. The staggered, drawn-out opening is now history.

If you'd like a deeper dive into how this might alter trading strategies, volatility, or liquidity patterns — especially during today's transition — just say the word.

Thanks for that.

That does change a few things for me so I'll need to read a bit more.

So is 9:59-9:59:15 the actual match (open price) or does that happen at 9:59:45-10:00am?

Also, the post-close continuous session - when does this finish?

And is closing price based off that or the actual 4:10 closing price and the new session count toward pre-market for the next session?