BSIP Dating Policy

This dating policy is used in the cataloguing of all sources.

The BSIP iconography database has been created to support musicology research and analysis. Many institutions specify their estimated dating in a manner where the start and end dates are not aligned with decades or centuries from a numerical perspective. For instance, a century may be defined as 1301-1400. Whilst this quite reasonable for the purpose for which they intend, it does not work well for statistical analysis and aggregation. We therefore need to avoid a date of 1400 creating an aggregation such that something dated 1301-1400 is then aggregated into 1400-1499. Different institutions operate different dating policies, sometimes giving undated works spans of the creator's lifetime, some using the creator's birth + 10 years and so on. Sometimes decades and five year periods are specified as 5-10 and 10-20, which in simple terms express 6 year and 11 year periods, and leaves us with the situation where the 1960s refers to 1960-1969 and 1960-1970 refers to the same time period.

This policy lays out how dates for sources obtained from institutions shall be modified to better reflect their intention and to be compatible with digital  analysis and aggregation using the data in the BSIP database. All dates will be normalised according to the guidelines set out below.

This policy should be used for estimated dates, and includes generating a more realistic date range based on an creator's lifespan than simply using their birth and death dated. A death date should be used explicitly and not altered unless it is known the creator could not have produced work in that period (see below).

Where dates are given in words the following will apply:

Term Dating to be applied
 Century xx00–xx99
 First quarter xx00-xx24
 Second quarter xx25-xx49
 Third quarter xx50-xx74
 Fourth quarter xx75-xx99
 First half xx00-xx49
 Second half xx50-xx99
 Early xx00-xx24
 Mid xx25-xx74
 Late xx75-xx99
 Late - Early xx75-xx24
 x0s (decade) xxx0-xxx9


Generic date ranges can of course be modified by the birth and death dates. Sometimes institutions will provide a generic date range whilst also specifying the creators whose lifespans are known. In these circumstances the generic range should be modified to reflect the narrowest period known.

The earliest date can be modified where a work is after another work and the date of production of the copied work is known.

Modifications to other dates where a generic date range has been provided in order to avoid crossing 5 year boundaries. So dates given as 1701-1800 should be changed to 1700-1799. This should also be done for decades 1750-1760 should become 1750-1759, and also with 5 year periods such as 1525-1530 should be 1525-1529.

The basis for the dating should be the narrowest period (so the latest earliest date, and the earliest latest date). Dates may also be further reduced by the following methods:

  • Known active dates
  • Lifetimes: Earliest birth date + 15 years ->  latest death date

Additional information should be taken into account, and care should be taken not to modify dates which fall quite legitimately on 5 years boundaries.

All changes to date ranges will be noted on the source under "Dating Sources" and will refer to this policy as "BSIP Dating Policy" when these modifications have been applied.

Barry Pearce
Aug. 2020