All posts by Rupert

The problem with dates

This is prompted by a question that arose during a meeting for ArtUK’s project to pilot the automatic updating of data on their website by speaking directly to the databases of contributing organisations – but it’s not really about that, fascinating and welcome as the project is. At some point in the discussion the question of dates came up, and this reminded me of something that’s been bugging me for some time: have museums been recording their dates properly? It’s a matter I raised a couple of years ago in the users’ email list for the collections management system I use at the National Gallery, Gallery SystemsTMS – where it was met with a resounding silence.

Let me explain. Most museum collections management systems allow users to record dates in two ways: as free text (sometimes called a ‘display date’), which could be as vague as ‘early fifteenth century’ or as specific as ‘2 February 1976’; and as a properly machine-readable date (or dates), following a standard format. The format that they use is almost always that mandated by ISO 8601, Data elements and interchange formats – Information interchange – Representation of dates and times.

An engraving by Hans Sadeler of a Gregorian perpetual calendar
Johann Sadeler I (1550-1600), Kalendrivm Perpetvvm (Gregorian perpetual calendar, with the Four Seasons), 1595, engraving on paper, 317 × 242 mm; Amsterdam, Rijksmuseum, RP-P-OB-7498. Photo: Rijksmuseum CC0 Public domain.

The formatting element of ISO 8601 is quite simple; of the variants it offers, the one most often used in museum software is the basic YYYY-MM-DD (which can be reduced down to as little as YYYY for less precise dates). The problem is to do with calendars. ISO 8601 specifies that dates should be recorded using the Gregorian calendar – the calendar in use in much of the world today, first introduced in some countries on 15 October 1582 as a result of reforms instigated by Pope Gregory XIII, and designed to reduce the disjunction between astronomical time and calendar time that had crept into the previous Julian calendar because of the way that leap years were calculated: the Julian calendar was by then 10 days adrift of astronomical time. In other words, when the Gregorian calendar was first adopted, 4 October 1582 was, in some countries, immediately followed by 15 October 1582. (The days of the week, however, ran on in their normal sequence.) The calendar was adopted across the world gradually: it only came into use in the British Isles in 1752, when 2 September 1752 was followed by Thursday 14 September 1752 (after me, now: ‘Give us our eleven days!’)

Detail from William Hogarth's 'An Election Entrtainment', showing a bully and a placard reading 'Give us our Eleven Days'
Detail from William Hogarth (1697–1764), An Election Entertainment, Plate I, 1755-8, engraving on paper; New Haven, Yale Center for British Art, Paul Mellon Collection, B1981.25.1448. Photo: Yale Center for British Art, open access.

But what about dates before 15 October 1582? According to ISO 8601, these can only be recorded ‘by mutual agreement of the partners exchanging information’; they should be recorded using the proleptic Gregorian calendar, which simply extends the Gregorian calendar back in time before its creation. This means that the precise dates of events that took place in the past should be shifted accordingly when entered into museum databases, if they are actually to adhere to the standard they profess to use. For example, Titian’s Bacchus and Ariadne arrived at its destination, Ferrara, on the Julian calendar date of 20 January 1523 (or thereabouts) – or 30 January in the proleptic Gregorian calendar.

Titian, Bacchus and Ariadne
Titian (active about 1506; died 1576), Bacchus and Ariadne, 1520-3, oil on canvas, 176.5 × 191 cm; London, The National Gallery, NG35, bought, 1826. Photo © The National Gallery, London Creative Commons License This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

I’d like to ask anyone reading this who works in museum documentation: are you really recording pre-Gregorian dates in ISO 8601-formatted fields using the proleptic Gregorian calendar – or are you just using the Julian calendar, and formatting your dates to look like ISO ones?

I can understand why museums might not be implementing ISO 8601 properly. For one thing, it means that the proleptic Gregorian date needs to be calculated every time you enter a Julian date. For another, it leads to problems when we consider anniversaries. The Wikipedia article on the Gregorian calendar discusses the supposed coincidence of the deaths of both Cervantes and Shakespeare on 23 April 1616 – although, as Spain at that time used the Gregorian calendar, and England the Julian, Cervantes actually died ten days before Shakespeare, the interval by which the two calendars diverged in 1616. But in 2020, we will mark the anniversary of Shakespeare’s death on its calendar date, 23 April, and not 404 years (of 365/366 days) after it actually took place, on 3 May. In other words, our anniversaries are out of step with our calendars if the events being commemorated occurred under the Julian calendar. And museums, as memory institutions, do like to mark anniversaries – even more so when there are social media accounts to feed with regular content. To return to the example of the Titian painting I mentioned earlier: when should we tweet the anniversary of its arrival in Ferrara – on 20 January (Julian date) or 30 January (ISO 8601 date)?

But if we stick with Julian calendar dates entered using the ISO YYYY-MM-DD format, we’re setting ourselves up for further problems when we come to calendars where the new year doesn’t fall on 1 January. Many European states – including England and, before 1600, Scotland – marked the new year on Lady Day (the Feast of the Annunciation, 25 March). So in England, for example, 31 December 1602 was followed immediately by 1 January 1602, and 24 March 1602 by 25 March 1603. If we were to write these dates using the ISO format, and list them in chronological order, we would end up with the sequence:

  • 1602-12-31
  • 1602-01-01
  • 1602-03-24
  • 1603-03-25

Why does this matter? First of all, there’s the problem of putting chronological dates in order: YYYY-MM-DD dates should sort nicely, as they’re arranged in order from largest to smallest component. But they don’t, if the year doesn’t begin neatly at YYYY-01-01. Secondly, there’s ample scope for confusion: James VI of Scotland succeeded to the throne of England as James I, bringing about the Union of the Crowns, upon the death of his cousin Elizabeth I late on 24 March 1603 by the Scots calendar – but 24 March 1602 by the English. (To resolve the ambiguity, dates are sometimes written using the conventions ’24 March 1602/3′, or ’24 March 1602 Old Style (O.S.)’ / ’24 March 1603 New Style (N.S.)’.) In the United Kingdom, all this – the date of the new year and the divergence between the Julian and Gregorian calendars – was resolved by the Calendar (New Style) Act 1750.

Attributed to Paul van Somer, James VI and I
Attributed to Paul van Somer (circa 1576–1621), James VI of Scotland and I of England, circa 1618, oil on canvas; New Haven, Yale Center for British Art, Paul Mellon Fund, B1982.18. Photo: Yale Center for British Art, open access.

And – if you’re not already banging your head on your desk in despair – ISO 8601 also creates a discrepancy with dates BC. The Julian calendar, as conventionally reckoned (remember, the Romans didn’t know to mark the birth of Christ in the year in which it occurred) included no year 0: 1 BC was followed immediately by AD 1. This is the convention followed in most historical texts. But the proleptic Gregorian calendar as used by ISO 8601 includes a year 0, with dates before that given negative numbers, and dates after (dates AD) given positive ones. So Julian 1 BC is in fact proleptic Gregorian 0, Julian 2 BC is proleptic Gregorian -1, etc.

So I can understand why museums might not actually be adhering to the standard that they profess to be using when they record dates. And with that happy thought I’ll sign off. For those of you who like to do things the old-fashioned way (and have some Italian), I find Adriano Cappelli, Cronologia, cronografia e calendario perpetuo: dal principio dell’era cristiana ai nostri giorni, 7th edn, Manuali Hoepli (Milan: Ulrico Hoepli, 1988, and reissued subsequently), ISBN 88-203-2502-0, a useful compendium of calendar-related information. My copy came with a calendar conversion program on 3.5″ floppy disk (remember them?), which I can’t get to run on Windows 10; fortunately, there’s now a superfluity of calendar converters online – John Walker’s, available here, has the added advantage of downloadable code that you can install locally should you wish.

Now, back to working out how to record fifteenth-century dates from Florence (using the Julian calendar and starting the New Year on Lady Day) in my collections management system.


  • 17 February 2020: erroneous references to ISO 8901 corrected to ISO 8601 (thanks to @gndnet).
  • 17 February 2020: erroneous reference to a 3¼″ floppy disk corrected to 3.5″ (thanks to Michael Comiskey).
  • 18 February 2020: there’s a more extensive discussion of these issues in Miranda Lewis, Arno Bosse, Howard Hotson, Thomas Wallnig & Dirk van Miert, ‘II. Standards: Dimensions of Data. 3. Time’ in Howard Hotson & Thomas Wallnig (eds.), Reassembling the Republic of Letters in the Digital Age: Standards, Systems, Scholarship (Göttingen: Göttingen University Press, 2019) DOI:10.17875/gup2019-1146, pp. 97-117 (thanks to Arno Bosse).

Dublin: kiosks, linked data, and the Dead Zoo

This April I was in Dublin for a few days, speaking at Collective Imagination 2019, the conference for users of TMS museum collection management software. This is a brief post about the conference and my lecture, and a visit to the Dublin Museum of Natural History.

Continue reading Dublin: kiosks, linked data, and the Dead Zoo

Send me your loan forms!

We’re coming up to the autumn conference season, and once again I’ll be going to the annual conference of CIDOC, the international committee for documentation that forms part of ICOM, the International Council of Museums – this year it’s in Heraklion, in Crete. Before the conference proper, I’ll be running a workshop on Sunday 30 September, along with colleagues from CIDOC’s Documentation Standards Working Group, for developers of digital collections management systems, focussed on the development of ‘EODEM’, an Exhibition Object Digital Exchange Mechanism.

We plan to kick off the development of a mechanism that lets users of different collections management systems share as easily as possible the information about their objects, and those objects’ requirements, that is needed when objects are lent from one institution to another. The lender should be able to just press a button to share the data, and the borrower just press another to import it into their system. This would eliminate a huge amount of the retyping that goes on when different museums exchange information about objects that they are lending and borrowing.

First, though, we need to identify the information that museums need to share. We’ll base the core information that identifies and describes the objects themselves on an existing standard, Object ID; but we need to know what information museums needs to share about borrowed objects’ requirements.

And here’s where I hope you can help us: the easiest way to do this will be for us to look at the information different museums request when they borrow objects. This is often requested using a ‘loan object information request form’, which the lending museum is asked to fill in for each object, giving its environmental needs, minimum security levels, etc. We’d like you to send us a copy of your museum’s ‘loan object information request form’ (blank, of course: we really don’t need sensitive individual object information, just the empty form so we can understand what you need to know). Drop me a line in the comments box at the foot of this page, and I’ll email you an address you can send the form to.

Once we have the forms, my colleagues and I will collate them all, draw up a list of the different pieces of information museums are asking for, and pass it to the system developers to incorporate into EODEM.

If all goes according to plan, future generations of registrars, exhibition organisers, and documentation staff will be forever in your debt!

The Encyclopaedia of Museum Practice

I’ve just (well, the month before last – but in terms of my writing on this site, that counts as ‘just’) got back from Tbilisi, the capital of Georgia, where I was attending the 2017 annual conference of CIDOC, the international organisation for those working in museum documentation.1 As well as a fascinating range of papers from many countries, visits to Georgian museums (and opportunities to sample Georgian wines), I facilitated a couple of sessions dedicated to the CIDOC Documentation Standards Working Group (DSWG)’s Encyclopaedia of Museum Practice – ably helped by my co-facilitators, Maija Ekosaari and Jan Behrendt, and filling in for the DSWG’s co-chair, Jonathan Whitson Cloud.

Continue reading The Encyclopaedia of Museum Practice

  1. I’ve also written about the 2014 CIDOC conference, in Dresden, and the 2016 conference in Milan. []

Magnificence: a very short introduction

I was shocked to realise that I received my Ph.D. twenty years ago this year. Because the subject I chose – an examination of the writings on art and architecture of the Bolognese notary and author Giovanni Sabadino degli Arienti (c. 1443-1510) – divided neatly into two halves, it was never really book-shaped, and so the only real publications I’ve managed to extract from it over the years were my Apollo article on looking at coins (which I wrote about recently here),1 and two articles in books, based on the second half of the thesis, which dealt with the concept of magnificence.2

Continue reading Magnificence: a very short introduction

  1. Rupert Shepherd, ‘A Letter Concerning Coins in Sixteenth-century Ferrara’, Apollo, Volume CXLIX, Number 443 (New Series) (January 1999), pp. 40-43; full text. []
  2. Rupert Shepherd, ‘Giovanni Sabadino degli Arienti and a Practical Definition of Magnificence in the Context of Renaissance Architecture’, in Mary Rogers and Francis Ames-Lewis eds, Concepts of Beauty in Renaissance Art, (Aldershot: Ashgate, 1998), pp. 52-65; Rupert Shepherd, ‘Republican Anxiety and Courtly Confidence: The Politics of Magnificence and Fifteenth-Century Italian Architecture’, in Michelle O’Malley and Evelyn Welch, eds, The Material Renaissance: Costs and Consumption in Italy, c.1400-1650, (Manchester: Manchester University Press, 2007), pp. 47-70. []

A note about an article about a letter about looking at coins

A few months ago, I received an email via the contacts page on this website from Franco Saetti, an Italian numismatist, asking me to send him a copy of an article [5 MB PDF] I had written many years ago, discussing a letter which describes a group of people looking at, and discussing, newly-minted coins in Bologna in 1505.1

I scanned a copy of the article and sent it to Ing. Saetti. I was delighted to receive a packet from him a few weeks later, containing a couple of offprints of his own which discussed the same coins as my article.2 I read Ing. Saetti’s articles with interest, and they led to some further thoughts about my article. Continue reading A note about an article about a letter about looking at coins

  1. Rupert Shepherd, ‘A letter concerning coins in sixteenth-century Ferrara’, Apollo, new ser., 149/443 (January 1999), pp. 40-43. []
  2. Franco Saetti, ‘Immagini prospettiche nella monetazione rinascimentale italiana: il doppio ducato di Alfonso I d’Este, Rivista italiana di numismatica e scienze affini, 101 (2000), pp. 113-137; id., ‘“Prove” in rame di monete del rinascimento italiano con ritratto’, Rivista italiana di numismatica e scienze affini, 116 (2015), pp. 329-358. []

Too much information: a CIDOC blog post

I’ve been keeping quiet about what I’ve been doing since starting work as Collection Information Manager at the National Gallery in February last year: much has been routine, and I was still planning the more ambitious part of my work, the Gallery’s Collection Information Project. But the project is now underway, with a project manager and data wrangler both now at work.

However, rather than post something here, I’ve taken the opportunity of an invitation to write a piece for the blog that has just been set up by CIDOC, the international organisation for museum documentation, to describe the problems that we face at the Gallery, and how the Collection Information Project plans to solve them. You can read it here.

A day of #MuseumDocumentation

Every now and again, a cry of anguish from appears on Twitter from Mark Carnall, Life Collections Manager at Oxford University Museum of Natural History, labelled with the #MuseumDocumentation hashtag. This is hardly surprising: like most of us who work in documentation, particularly those dealing with collections which have built up over a period of time, Mark often has to deal with multiple object records of variable quality.

Last Friday, he decided to live tweet a day spent cleaning reptile records in multiple databases (as he points out, one of these was a Word document, which really does stretch the definition of ‘databases’). Because this gives a nice insight into the kinds of problems that many of us face at regular intervals, I’ve Storifyed his tweets for posterity; you can read them here. As you will see, in addition to the usual difficulties caused by a collection’s documentation ‘evolving’ over time, natural history collections seem to suffer from some particular problems of their own – including the (to me) surprisingly fluid nature of many scientific names.

One month, five events

July was a busy month – so busy, that I’ve only now finished writing up notes from the five different conferences, workshops and meetings that I attended in just over three weeks. But why spend so much time out of the office? Continue reading One month, five events

Captain Colbeck’s plaque

Further to my piece on Captain Colbeck’s eggs, I was delighted to be invited to the unveiling of a plaque in memory of William Colbeck on the site of his old house at Inchmery Road in Catford, south-east London. Organised by Sandra Margolies, Colbeck’s grand-daughter, the event was attended by many of Colbeck’s descendants – as well as relatives of his former shipmate on the SY Morning, Alfred Cheetham, and of E. A. Wilson, the zoologist and junior surgeon on the Discovery expedition and chief of the scientific staff on the Terra Nova expedition.

Memorial plaque to William Colbeck
Memorial plaque to William Colbeck, Inchmery Road, Catford

There were speeches by Kate Richardson, of the Culverley Green Residents’ Association; Donald Lamont, chairman of the UK Antarctic Heritage Trust; and Sir Steve Bullock, Mayor of Lewisham. The plaque was ‘unveiled’ by Kevin Fewster, Director of Royal Museums Greenwich. Everyone was given copies of the burgee of the Pirate Yacht Club, Bridlington, taken by Colbeck on the Southern Cross expedition,  to wave.

The event concluded with a small reception, at which a rather spectacular cake, decorated with penguins (identified by David Wilson as baby Emperors and adult Gentoos), was served.

Cake served at the unveiling of a memorial plaque to William Colbeck
Cake decorated with penguins, served at the unveiling of a memorial plaque to William Colbeck