How many trading sessions fit inside a 61 day wash sale window

Answered against 22 years of US equities and 12 years of US options data and published with the query that produced it. This result is stored as of 2026-08-13, from Wash Sale Rule and Options: The 61-Day Window.

Rows × columns

30 × 4

Period covered

2024-01-01 to 2026-06-01

Computed

2026-08-13

Completeness

No missing values

Source

US exchange, SIP and OPRA market data

Licence

Strasmore terms · free, no signup

Formats

JSON · CSV · the SQL below

What each column holds

Computed from Strasmore's warehouse of US exchange, SIP and OPRA market data. Equity prices are delayed; options greeks and implied volatility are end-of-day. This result is stored, not recomputed on load — it is exactly the numbers that were returned on 2026-08-13, and the query below is what returned them.

WITH sessions AS
(
    SELECT DISTINCT date AS d
    FROM global_markets.stocks_daily_aggs
    WHERE ticker = 'SPY'
      AND date >= '2023-11-01'
),
month_ends AS
(
    SELECT
        toStartOfMonth(d) AS m,
        max(d)            AS anchor
    FROM sessions
    WHERE d >= '2024-01-01'
      AND d <  '2026-07-01'
    GROUP BY m
)
SELECT
    toString(me.m)                                            AS month,
    toString(me.anchor)                                       AS last_session,
    countIf(s.d >= me.anchor - 30 AND s.d <= me.anchor + 30)   AS sessions_in_window,
    61                                                        AS calendar_days_in_window
FROM month_ends AS me
CROSS JOIN sessions AS s
GROUP BY me.m, me.anchor
ORDER BY me.m