Direct answer
The “start of the Asian forex session” is typically defined as the point when trading activity is considered to enter the Asia-based trading hours, most often aligned with the Tokyo time window. There is no single universal start moment, because different market calendars and platforms may use slightly different cut-off times and time zones.
How the “start” is defined (and what to expect)
In liquidity-by-session terms, the Asian session is the period when participants tied to Asian time zones are most active, which commonly concentrates around Tokyo business hours. To interpret “start,” you need two assumptions:
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A session definition exists in your reference source. One calendar may define the Asian session start earlier or later than another, even if both are “Asia” focused.
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A time zone is chosen. Forex is traded globally, so the same moment can correspond to different local times depending on whether you track the session in Tokyo time, UTC, or your own local time.
Because of these differences, a practical way to state the answer is: the Asian forex session starts when your chosen reference marks the beginning of the Tokyo-focused trading window, and that boundary can vary by tool.
Example checks you can do independently
Here are ways to verify the start time without assuming a single universal rule:
- Compare session calendars: Pick two independent market-hour calendars and note their Asian session start boundaries in the same time zone (for example, convert both to UTC before comparing).
- Check your trading platform’s session markers: Many platforms display session labels or implied schedule boundaries; use those labels as your operational definition.
- Look for liquidity build-up: In real markets, activity may increase slightly before the exact boundary and then fluctuate after it. That means “first liquidity” and “official session start” can differ.
Limitations and uncertainty
- Session start times are convention-based: Different sources can define the start at different clock times.
- Time zone conversion matters: Converting to UTC (or another consistent reference) reduces confusion.
- No real-time prediction: The start boundary describes timing conventions and typical activity windows, not a guarantee of market behavior.
If you need a single clock time, use one reference (calendar or platform) and convert its “Asian session start” into your desired time zone. That approach keeps the definition consistent with your data.