™A purchase 30 calendar days after a loss sale lies inside the +30-day side; day 31 lies outside that side, without resolving other purchases or identity questions.
Taxes & Account Rules
Wash-sale window
The period from 30 calendar days before through 30 calendar days after a loss sale, including the sale date.
Plain-English context
Put the definition to work.
Use calendar days before as well as after. Checking one day pair does not resolve every acquisition or matched lot.
Further reading and verification. Examples are hypothetical, not current quotes or recommendations. Product terms, tax treatment and market rules can change. IRS Publication 550 — investment income and expenses