Most people don’t think of time as a legal topic, but it’s hard to imagine what any of our societies would look like if our laws never mentioned any measures of time. A recent article in Studia Canonica (A. Marcello, “The Computation of Time: A Canonical Overview,” Studia Canonica 51 , 207–250) explored the canonical history of computing time. I thought I’d take a few moments to explore the fun problem of birthdays and leap day birthdays (Feb. 29) from a legal perspective.
If one is not familiar with the reasons for a leap day, in a nutshell, it’s because the actual time it takes the earth to orbit the sun once (tropical year) is 365 days 5 hours 48 minutes 46 seconds. Our calendar has 365 days per year. How do we account for the accumulation of those extra hours, minutes, and seconds? A leap day every four years (with periodic exceptions because four times 5 h. 48 m. 46 s. is slightly less than 24 hrs.)
The question of computing time was first tackled by ancient Roman jurists. Roman law established that a day is a 24 hour period measured from midnight to midnight (cf. Dig. 2.12.8 (Paulus, Ad Sabinum 13)) and that the law recognizes days only as whole units: a partial day must either be reckoned a whole day or no day (cf. Dig. 50.16.134 (Ulpian, Ad legem Iuliam et Papiam 2)). Additionally, a period of time is not considered over until the last day in the count has entirely expired (cf. Dig. 44.7.6 (Paulus, Ad Sabinum 4)). These principles established themselves in European legal thought and found their way into the modern day civil law and common law traditions. With respect to computing time, at least, common law, civil law, and canon law have only a few differences.
The principles of canonical computation as laid out in the current Code of Canon Law and the Code of Canons of the Eastern Churches are basically identical to the principles followed by the modern civil law tradition. Compare, for example, 1983 CIC can. 200–203 and 1990 CCEO can. 1543–1546 to France’s Code of Civil Procedures, art. 641–42; Italy’s Code Civ. Proc., art. 155; Germany’s Civil Code, sec. 187–188, 191; and to the codes of civil procedure of Quebec and Louisiana, two civil law jurisdictions in countries following the common law tradition (cf. Qc. Code Civ. Proc., art. 8; La. Code Civ. Proc., art. 5059). Turning to the common law (I’m using American common law as my example) we find the same basic principles. “The law [takes] no cognizance of fractions of days” (US v. Wrigtht, 197 F 297 (8th Cir. 1912)). Additionally a day is considered to be the period of 24 hours from midnight to midnight (cf. Talbott v. Caudill, 248 Ky. 146, 58 S.W.2d 385 (Ky. Ct. App., 1933)). Lastly, “where the common law prevails, the general rule for the computation of time is to exclude the first and include the last day” (People v. Woolfolk, 304 Mich App 450; 848 NW2d 169 (Mich. Ct. App., 2014)).
That brings us to topic of calculating one’s age. One’s age indicates the number of full years one has completed since the moment of one’s birth. So if, for example, Jack is born on 2:31 PM on 1 Jan. 2018, he’ll turn one year of age on 2:31 PM on 1 Jan. 2019, two on 1 Jan. 2020, etc. Pretty simple. The problem is that the legal principle is that parts of days don’t count. Either it counts as a whole day or it counts as no day. Going back to our example, that means the law considers Jack to have been born either at 12:00 AM, 1 Jan. 2018 (if 1 Jan. counts) or (if 1 Jan. doesn’t count) 12:00 AM, 2 Jan. If Jack was “legally” born midnight on 1 Jan., then a year’s period will end at 11:59 PM on 31 Dec. If Jack was “legally” born midnight on 2 Jan., then Jack finishes a year at 11:59 PM on 1 Jan.
However, it’s not that simple. Remember, days are either whole days or no days. There is no difference between something that happens at 12:00 AM and something that happens at 11:59 PM; legally speaking they happened at the same time. So, when does Jack turn one year old? 12:00 AM on 31 Dec. (because he completes one year at 11:59 PM, 31 Dec., because he was “legally” born at 12:00 AM, 1 Jan.) or 12:00 AM on 1 Jan. (because he completes one year at 11:59 PM, 1 Jan., because he was “legally” born at 12:00 AM, 2 Jan.)
Canon law and the civil law tradition address this dilemma by, first, not counting the birth day and, second, by understanding that when the law says a year, it means a complete year and change. So, in our example, if Jack’s age were calculated according to canon law or the civil law tradition, he turns a year only after 12:00 AM, 2 Jan. (See, e.g. 1983 CIC can. 1083 §1 and France Civ. Code, art. 144 that speak of the completion of age necessary to marry.)
The common law does something different, and on top of that it does not have a uniform approach. Some jurisdictions follow the traditional common law rule, which is to count the birth date. A more recent approach taken by other common law jurisdictions is to not count the birth date (the so-called “birthday rule”). In both cases—following the principle originally laid down in Roman law (cf. Dig. 28.1.5 (Ulpian, Ad Sabinum 6))—a person turns a year at midnight of the day prior. So if, for example, our friend Jack lived in Missouri (which follows the traditional rule), he would legally turn a year on 12:00 AM on 31 Dec., but if he was lived in California (which follows the “birthday rule”), he would legally turn a year at 12:00 AM on 1 Jan (his birthday!).
Now that we’ve settled that, what about Jack’s older sister Amy who was born at 6:21 AM on 29 Feb. 2012? When does she turn a year older?
One approach to leap days is simply to ignore them. According to Roman law anything that happened on the leap day legally happened on the day prior (cf. Dig. 50.16.98 (Celsus, Libro digestorum 39)). Even if one doesn’t ignore it, leap day birthdays aren’t actually that problematic for legal computations of time. In the canonical and civil law traditions, her birth date did not count so she was not “legally” born until 12:00 AM, 1 Mar. 2012. Therefore, she completed her first year at 12:00 AM, 1 Mar. 2013, her second on 1 Mar. 2014, etc. Likewise, common law jurisdictions that follow the traditional rule have no problem. Amy was “legally” at 12:00 AM, 29 Feb. 2012 and turned one at 12:00 AM, 28 Feb. 2013, two on 28 Feb. 2014, etc.
What about common law jurisdictions that follow the “birthday rule”? In that case, Amy’s year started at 12:00 AM, 1 Mar. 2012 and ends at midnight the day prior to 1 Mar. 2013, that is 12:00 AM, 28 Feb. 2013 (except on leap years in which case it’s 29 Feb.). This is the same wrinkle that the canonical and civil traditions have for birthdays on 28 Feb. 2012. That year period started at 12:00 AM, 29 Feb. 2012 and was completed at 12:00 AM, 1 Mar. 2013 (except on leap years in which case it completes on 29 Feb.).
In the end, leap days are not that big of a deal because the law has a flexible definition of a year. It’s 365 days unless it needs to be 366. If lawmakers want 365 days and only 365 days, they write the law to say 365 days instead of saying one year. (Eg. a year prison sentence which ran through Feb. 2012 is one day longer than a 365-year prison sentence that ran through Feb. 2012.)