Direct answer
Information about forex “session overlaps” can be verified by (1) defining the overlap precisely as a time interval, (2) using the same session window definitions and time-zone/DST assumptions as the source, and (3) reproducing the overlap calculation from the stated inputs. Because different websites and providers define sessions differently, verification is mainly about checking the methodology, not about trusting a single published chart.
Mechanism or definition
A session overlap is a period when two (or more) named market sessions are open at the same time. To verify any “overlap” statement, rewrite it into a calculation:
- Pick two sessions, A and B.
- For each session, define its open and close times as clock times in a specified time zone.
- Convert those times consistently into one reference time zone (for example, UTC) using the stated assumptions about daylight saving time (DST).
- The overlap window is the intersection: from max(A_start, B_start) to min(A_end, B_end).
- If the computed start time is earlier than the computed end time, overlap exists; otherwise, it does not.
Stable mechanics here are the intersection-of-intervals idea. What varies is the input: how a “session” is defined (hours, cut-off times, whether the label reflects liquidity vs trading hours), and which time zone rules are applied.
Evidence or example (reproducible steps)
Since no real-time data is required, you can test a claim using a reproducible, offline method.
- Extract the source’s assumptions
- Write down the exact session windows it uses (start and end times), including the time zone.
- Note any DST handling rule (for example, “local time including DST”). If the source does not state this, treat the claim as incomplete.
- Standardize time
- Convert all session boundaries into the same reference time zone.
- Use the same conversion for both sessions, for the same date range mentioned in the claim.
- Compute overlap
- Apply the intersection rule: overlap_start = max(A_start, B_start), overlap_end = min(A_end, B_end).
- If overlap_end ≤ overlap_start, the overlap window is empty.
- Check sensitivity
- Repeat the calculation with any alternative DST interpretation or alternative session cut-off times shown by another reputable reference.
- If the overlap duration changes materially (for example, overlap appears/disappears), the “overlap” is dependent on definitional assumptions.
- Validate with independent clocks
- Compare the resulting overlap window against a calendar/time-tool that tracks time zones for the same date.
- This does not “prove” liquidity changes; it verifies that the stated overlap times match the chosen time rules.
If the source shows a chart, you can also cross-check by sampling a few dates where DST changes occur—overlap claims often fail verification specifically around DST boundaries.
Limitations and risks
- Definitions differ: providers may use different session hours or different meanings of “open,” so two sources can both be consistent with their own definitions while disagreeing.
- DST uncertainty: if a source omits DST assumptions, the overlap window can shift by one hour depending on the date.
- Cut-off and broker differences: “session hours” may be calendar-based, while actual tradability depends on platform execution, spreads, and access rules; historical overlap does not imply identical future execution conditions.
- No guarantee of market effects: even if two sessions overlap in time, the magnitude of liquidity or volatility can vary with market conditions.
A material failure mode is relying on a visual overlap chart without confirming the underlying session start/end times and the time-zone conversion rules.
Verification or next question
Before accepting any statement about session overlaps, ask: “What exact session windows, in what time zone, and under which DST rule were used?” Then reproduce the overlap calculation using those inputs. If you want to go further, compare the overlap definition across at least two independent references and document where the assumptions differ—because that difference is usually the root of conflicting overlap claims.