Definition
A Latin term from Roman civil law meaning to introduce or insert something among or between other things. In legal usage, the term refers specifically to the insertion of a day, month, or other unit of time into the calendar — the act of intercalation. The concept captures both the general act of interpolating something into an existing sequence and the particular calendrical practice of adding supplementary time units to reconcile the legal or civil calendar with the solar year.
Why It Matters in Research
INTERCALARE appears almost exclusively in primary Roman law sources and in legal dictionaries that translate or annotate civil law materials. Researchers encountering this term will most commonly find it in discussions of the Digest (Justinian's Digesta), specifically Dig. 50, 16, 98, pr., which is the passage all major historical dictionaries cite as the locus classicus. That passage falls within the De verborum significatione title — a section devoted to the legal meaning of words — signaling that the term carried definitional weight in Roman jurisprudence, not merely descriptive usage.
The practical legal significance of intercalation in Roman law was substantial. The Roman calendar was periodically adjusted by the insertion of intercalary days or months (notably the intercalary month Mercedonius under the pre-Julian calendar). Legal deadlines, statutes of limitation, and the computation of prescribed time periods all depended on an agreed calendar. Disputes about whether an intercalary period counted toward a limitation period, or whether a contract term had elapsed, required courts to understand precisely what intercalare meant and when intercalation had occurred. Researchers tracing time-computation doctrines in civil law jurisdictions back through canon law, medieval civil law commentary, and Roman sources will encounter intercalare as part of that background.
This term essentially vanishes from Anglo-American common law sources because English law developed its own time-computation rules without reliance on Roman calendrical vocabulary. Researchers working in comparative law, Roman law, or Louisiana and Quebec legal history (jurisdictions with civil law foundations) are the most likely to need this entry. In those contexts, intercalare may surface in annotated translations of Roman texts, early treatises, or commentary on civilian codifications.
Note also that Black's 1st edition contains an erroneous entry immediately preceding the INTERCALARE entry in some printings, where text about inter vivos gifts appears — a typographical artifact of the dictionary's organization. This does not affect the definition of INTERCALARE but may confuse researchers reading photographic reproductions of the original volume.
Historical Dictionary Support
The historical dictionaries are in complete agreement on this term. Black's (1st and 2nd editions), Burrill, and Bouvier all define INTERCALARE identically: to introduce or insert among or between others; specifically, to introduce a day or month into the calendar. All four sources cite the same passage, Dig. 50, 16, 98, pr., as authority. No substantive disagreement or evolution of meaning appears across these sources.
Burrill adds the most etymological context, tracing the word to inter (between or among) and the Old Latin calare (to call), connecting it to the Roman practice of publicly proclaiming calendrical adjustments. This derivation is useful for understanding why the term carried official and legal weight in Roman practice — intercalation was not a private computation but a public act of the pontifical college, which held authority over the calendar before the Julian reforms.
What the historical dictionaries do not address is the downstream legal consequence of intercalation — that is, how Roman courts and jurists actually handled time-computation problems arising from intercalary periods. Researchers should not assume that defining the act of intercalation resolves the substantive legal questions it generated. For that, the Digest text itself and secondary scholarship on Roman legal procedure are necessary.
Jurisdictional Note
INTERCALARE has no meaningful presence in modern common law jurisdictions. Its relevance is confined to Roman law study, civil law jurisdictions, and legal history research. Modern statutory time-computation rules in civil law countries have long since displaced the need to reason directly from Roman calendrical vocabulary.