|BBIH Help - Table of contents||2.8.10 Period covered|
The Period covered field is available on the Simple search screen and on the Advanced search screen. On the advanced search screen, there is an additional option to limit your results to close matches.
The majority of pre-1946 publications have not been categorised using this field, so, if you use this field to restrict your search, most pre-1946 publications will be omitted (exceptions are works on Imperial and Commonwealth history, and data from Irish History Online and London's Past Online). Note also that records are categorised by period covered with varying precision; click here for more information.
To search, enter a range in years. Dates BCE (or BC) can be entered following a '-' sign (e.g. -55) although such dates will display as BCE in your search results; however, coverage of prehistoric material is not systematically recorded in the Period covered field, so the entering of dates earlier than 55 BCE is not recommended.
To search for a single year, enter the same date in both boxes. If you enter a year only in the first box, the software will search for the period from the date that you enter through to the present. If you enter a year only in the second box, the software will search for the period up to the date that you enter.
When you search by period covered records which overlap in any degree with your selected date range will be returned, so, if you enter the range 1660 to 1666, records indexed as covering 1664, 1665-90, 1650-1662, 1650-1672 and 1000-1700 will all be returned if they match your other search criteria. Note that:
• If you are interested in a long period, it may be best not to include in your range the earliest and latest dates in the range for which you wish to search. For example, entering 1500 to 1600 will include in your results all those records matching your other search criteria which have been catalogued as beginning in 1600 (which could include records covering 1600-1900, for example) and which have been catalogued as ending in 1500 (which could include records covering 1000-1500, for example). This means that if you are searching for works which deal with the sixteenth century in general, and are not specifically concerned with 1500 or 1600, the best results will be obtained by searching for 1501-1599.
• On the Advanced search screen you can obtain more precise results by ticking the Close matches only box. This excludes from your results any records whose period covered begins 100 or more years before the starting date that you specify, and any records whose period covered ends 100 or more years after the finishing date that you specify. This option will therefore exclude records covering very long periods that may touch only lightly on the particular period in which you are interested, and also any records whose period covered has been indicated only approximately. Bear in mind, though, that you nonetheless run some risk of missing worthwhile results if you use this option.
Hint for RHS Bibliography users: In the RHS Bibliography you could search using period covered only when you had also filled at least one other field. In BBIH you can, if you wish, search by period covered only.