Definition
The act of calculating, reckoning, or estimating a numerical result according to an established method. In legal contexts, computation carries a meaning more precise than mere arithmetic: it refers specifically to the legally prescribed method of measuring time or amounts, governed by rule of law rather than by the agreement or preference of the parties.
Two principal legal senses:
1. Computation of time. The formal legal accounting of days, months, or other time periods as required by law — determining, for example, on which day a statute of limitations begins to run, whether a deadline falls on a holiday or weekend, whether the first or last day of a period is included or excluded, and how a "month" is counted when no calendar month exactly applies. This is the dominant historical legal sense and appears throughout procedural rules governing notices, pleadings, appeal deadlines, and similar time-sensitive acts.
2. Computation of amount. The calculation of a legally defined sum — damages, taxes, wages, interest, or other monetary obligations — performed according to a formula or method prescribed by statute, regulation, or court rule. This sense is prominent in tax law, employment law, and damages calculations.
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Common Language
Modern common usage (Wiktionary): "The act or process of computing; calculation; reckoning" and "the result of computation; the amount computed."
Historical common usage (Webster's 1913): "The act or process of computing; calculation; reckoning" and "the result of computation; the amount computed."
The common meaning is essentially correct as far as it goes, but it is silent on the most important legal dimension: that legal computation is not free-form arithmetic but a rule-governed process in which law — not the parties, and not convenience — dictates how time or amounts are to be counted. A party who "computes" a deadline using ordinary calendar arithmetic but ignores the applicable procedural rule may reach a different and legally incorrect result.
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Common Confusion
Computation is sometimes conflated with mere calculation or estimation. The distinction matters: an estimate involves approximation and judgment; a legal computation applies a fixed legal rule to yield a determinate result. Where computation of time is at issue, parties cannot substitute a reasonable estimate or a mutually agreed method — the legal rule controls. Similarly, in tax and statutory contexts, computation according to prescribed tables or formulas is not interchangeable with a general approximation of the amount owed.
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Why It Matters in Research
The procedural stakes of computation of time are high and historically underappreciated. Researchers working in case law before the mid-twentieth century will find that courts were sharply divided on questions such as whether the terminal day of a limitations period counts, how a "month" is measured when the starting date has no equivalent in the target month, and whether Sundays and legal holidays are included or excluded. These disputes produced substantial litigation and are not resolved uniformly across jurisdictions or eras.
Modern procedural rules — such as Federal Rule of Civil Procedure 6 — have codified specific computation-of-time rules that resolve many of these questions, but those rules do not apply retroactively to historical cases, and many state systems have their own variants. Researchers interpreting older decisions must resist importing modern computational rules back into historical analysis.
In tax research, computation takes on its second major dimension: the application of rate schedules, tables, and statutory formulas to determine a precise liability. The Law Mind Tax Encyclopedia entries on tax tables and computation are directly relevant here. Tax computation research requires close attention to the applicable tax year and the specific version of the rate schedule in effect, since these change frequently.
A trap for researchers: older dictionaries and treatises treat computation almost exclusively as a matter of time-reckoning, reflecting the procedural preoccupations of common law practice. They give little or no attention to the computational mechanics of taxes or damages, which are largely twentieth-century developments. Do not assume that a historical source's silence on computation-of-amount reflects the full modern scope of the term.
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Historical Dictionary Support
The historical dictionaries converge strongly on computation as a legal discipline governing the measurement of time by rule of law. Bouvier and Burrill are in close agreement, both drawing on Cowell and Termes de la Ley, defining computation as "the account and construction of time by rule of law, as distinguished from any arbitrary construction of parties." The emphasis on distinguishing legal reckoning from party-chosen methods is consistent across all sources and reflects a genuine doctrinal concern of historical common law practice.
Rapalje and Lawrence, drawing from Termes de la Ley, add useful color: computation must be "true and indifferent" — neither favoring one party nor leaving time determinations open to arbitrary interpretation. This framing reveals that the concept was understood not merely as procedural mechanics but as a matter of legal fairness and equality.
Black's first edition offers a thin entry — "the act of computing, numbering, reckoning, or estimating" — that captures the general meaning without the specificity of Bouvier or Burrill. The second edition's relevant text is fragmentary in the source material.
None of the historical dictionaries address computation in the tax or damages sense, which is consistent with their era. Researchers should treat the historical sources as authoritative for time-reckoning questions but not as complete guides to the term's modern reach.
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Jurisdictional Note
Computation of time rules vary significantly by jurisdiction and court system. Federal courts follow FRCP Rule 6; state courts apply their own variants, which may differ on holiday exclusions, the counting of the first and last day, and treatment of electronic filing deadlines. International and admiralty contexts add further variation. When researching deadline disputes, always identify the specific procedural rule in force in the relevant jurisdiction and at the relevant time.
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Encyclopedia Cross-Reference
Tax Tables and Computation — The Law Mind Tax Encyclopedia
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