Laws of Time and Planets: Movable Feasts 2014

Perpetual Calendar from Guarini’s Leges Temporum

Leges temporum movable feasts editedGuarino Guarini, Leges Temporum, et Planetarum… (Turin: Ex Typographia Haeredum Caroli Ianelli, 1678): p. 3 of tables.
Source: Google Books / Bayerische Staatsbibliothek

Guarino Guarini’s Leges Temporum, et Planetarum… (Turin: Ex Typographia Haeredum Caroli Ianelli, 1678) presents an extensive set of astronomical tables specifically addressed to an audience in and around Turin. In fact, the title page explicitly lists the latitude and longitude for the Piedmontese capital. The tables include various calendars – Roman, Persian, Egyptian, and others – as well as lunar cycles and other astronomical phenomena. Cross-reference lists relate some tables to each other or to the calendar of the common era. Other tables furnish the latitude and longitude of cities in Italy and abroad. The publication is situated squarely within the tradition of early modern Catholic astronomy, chiefly directed to calculating the annual date of Easter and other movable feasts in the liturgical calendar.

Guarini looked far into the future, providing the necessary information to calculate Easter for many centuries after publication of the book. Even the new year 2014 is accounted for. After consulting initial tables which aid in determining the date of the first Sunday of the year, the lunar cycle in relation to the vernal equinox, and adjusting (if necessary) for a leap year, the reader is directed to “Tabula 10” (above), where the correct row for 2014 is underlined in red. The table gives the following values:

Movable Feasts for 2014 from Leges Temporum

“dominical (or Sunday) letter” = First Sunday of year: “e” = 5 January
Septuagesima Sunday: 16 February
Ash Wednesday: 5 March
Easter: 20 April
Ascension: 29 May
Pentecost / Whitsun: 8 June
Corpus Christi: 19 June
24 Sundays after Pentecost
Advent begins: 30 November

Here’s to a festive 2014!

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Further reading:

J. L. Heilbron, The Sun in the Church: Cathedrals As Solar Observatories (Cambridge, Mass: Harvard University Press, 1999).

Image below: Globe with eclipse diagram, from Guarino Guarini, Leges Temporum, et Planetarum… (Turin: Ex Typographia Haeredum Caroli Ianelli, 1678): 48.
Source: Google Books / Bayerische Staatsbibliothek

Globe Leges Temporum