Calendar seasonality as a regime filter, not a standalone signal

Industry holidays and monthly market seasonality

The discussion separates industry holiday cycles from market seasonality that can appear every month and sometimes twice a month. Monthly seasonality is defined as strength over the last couple of days of a month through the first couple of days of the next, a window sometimes labeled the turn of the month. Those sessions are often linked to mutual-fund and later exchange-traded-fund cash flows, and they are described as advances more often than not.

Editorial: read that monthly window as market-state context, not as a self-contained buy or sell. A seasonal-regime overlay uses the calendar to qualify a chart-based or portfolio-neutral hypothesis. It does not replace that hypothesis.

Calendar dates as rule inputs

Calendar dates are treated as rule inputs for entries, exits, and month-end flattening, including on market-neutral books. The workflow does not wait for every chart condition to quantify a buy or sell. Dates mark when a book may act, stand aside, or flatten. They are not a substitute for a repeatable price hypothesis.

Editorial: this is how monthly turns become testable alongside the rest of the book. The same calendar field that allows an entry can also force an exit or an abstention when the window closes.

Window dressing, year-enders, and January

Window dressing is framed as a quarterly reporting-period flow. When funds prefer recently strong names, that habit can add to monthly seasonality rather than sit apart from it. The two effects can stack at the same turn of the month when a reporting date and a month-end cash-flow window overlap.

Year-enders are described as buying a group of underperforming names before calendar year-end after late-November or early-December tax-loss selling. A 30-day wash-sale repurchase constraint is used to explain why those tax-sale names tend to be bought back in January, and why January can firm broader markets. In this vocabulary that follow-through is the January effect, and the wash-sale rule is the tax constraint that delays the repurchase.

Pre-holiday strength and a rejected weekday taboo

Historical review is said to show pre-holiday advances more often than not, including a late-year rally singled out in that review. A Monday-or-Friday selling taboo is explicitly rejected. Holiday timing and weekday folklore are not treated as the same kind of evidence.

Editorial: a pre-holiday rally is still only a supporting tendency. It can sit inside the seasonal-regime overlay. It is not a reason, on its own, to take a chart setup or to skip one.

Keep seasonality in a supporting role

Seasonal tendencies are assigned a supporting role in the decision process, not the primary reason to buy or sell. Readers are told to inspect roughly 75 years of history themselves. A seasonal chart pattern remains a separate claim about price structure. Editorial: put that single setup inside the seasonal context, then keep the calendar in its supporting role.