Here's another way to find invalid dates - this search query returns 200 BYU items that have no date value in the search engine:

http://www.archive.org/advancedsearch.php?q=sponsor%3A%22Brigham+Young+University%22+AND+NOT+date%3A1*+AND+NOT+date%3A2*+AND+collection%3Aamericana&fl[]=date&fl[]=identifier&rows=250&output=tables

Below is a metamgr query to show a histogram of the date values in all those items (long and ugly URL - sorry!). Some are legit - e.g., when the date isn't known, the MARC record may specify "[n.d.]" for the date, and that won't be considered valid by the search engine. But most of the values result from someone manually inserting something invalid.

http://www.us.archive.org/metamgr.php?f=histogram&group=date&w_identifier=pourunregard00mr%20OR%20pourvivre00goza%20OR%20prologdichtung00wern%20OR%20rponsedunefavo00minn%20OR%20traitepratiqueda02lewa%20OR%20stephensmonthlym00step%20OR%20streikbrecherfes00bern%20OR%20sundayschoolteac00sund%20OR%20supremepardon00lano%20OR%20undergraduatecat19941995brig%20OR%20undergraduatecat19951996brig%20OR%20undergraduatecat19961998brig%20OR%20undergraduatecat19971998brig%20OR%20undergraduatecat19981999brig%20OR%20undergraduatecat19992000brig%20OR%20undergraduatecat20002001brig%20OR%20undergraduatecat20012002brig%20OR%20undergraduatecat20022003brig%20OR%20undergraduatecat20032004brig%20OR%20undergraduatecat20042005brig%20OR%20undergraduatecat20052006brig%20OR%20undergraduatecat20062007brig%20OR%20undergraduatecat20072008brig%20OR%20traitepratiqueda01lewa%20OR%20wihenbergvorfunf00bern%20OR%20zeugnissefurdiee00reit%20OR%20zurlandesbefesti00zuri%20OR%20zustandewahrendd00wild%20OR%20zurallensteiners00somm%20OR%20vorfunfzehnjahre00leip%20OR%20uberdielagedesbu00hann%20OR%20classschedule19331934brig%20OR%20classschedule19401941brig%20OR%20classschedule19361937brig%20OR%20classschedule19561957brig%20OR%20classschedule19611962brig%20OR%20classschedule19411942brig%20OR%20classschedule19471948brig%20OR%20classschedule19511952brig%20OR%20classschedule19481949brig%20OR%20classschedule19351936brig%20OR%20classschedule19601961brig%20OR%2050griefsfaitsarg00laro%20OR%20adamgraemeofmoss00olip%20OR%20annualcatalogue19131914brig%20OR%20annualcatalogue19141915brig%20OR%20annualcatalogue19151916brig%20OR%20annualcatalogue19161917brig%20OR%20annualcatalogue19171918brig%20OR%20annualcatalogue19181919brig%20OR%20annualcatalogue19191920brig%20OR%20annualcatalogue19201921brig%20OR%20annualcatalogue19211922brig%20OR%20annualcatalogue19221923brig%20OR%20annualcatalogue19231924brig%20OR%20annualcatalogue19231926brig%20OR%20annualcatalogue19241925brig%20OR%20annualcatalogue19251926brig%20OR%20annualcatalogue19261927brig%20OR%20annualcatalogue19271928brig%20OR%20annualcatalogue19281929brig%20OR%20annualcatalogue19291930brig%20OR%20annualcatalogue19301931brig%20OR%20annualcatalogue19311932brig%20OR%20annualcataloguei19411942brig%20OR%20annualcataloguei19421943brig%20OR%20annualcataloguei19431944brig%20OR%20annualcataloguei19441945brig%20OR%20annualcataloguei19451946brig%20OR%20annualcataloguei19461947brig%20OR%20annualcataloguei19481949brig%20OR%20annualcataloguei19491950brig%20OR%20annualcataloguei19501951brig%20OR%20annualcataloguei19511954brig%20OR%20annualcataloguei19521953brig%20OR%20annualcataloguei19531954brig%20OR%20annualcataloguei19541955brig%20OR%20annualcataloguei19551956brig%20OR%20annualreportofro00roya%20OR%20apologyforbiblei00byuwats%20OR%20aristidebruant00mete%20OR%20ausdemfranzosenj002somm%20OR%20ausdemfranzosenj00somm%20OR%20ausdemildisschluss00somm%20OR%20ausdemteiliiidieflu00somm%20OR%20auslegungdesvate00luth%20OR%20ausmeinemkriegst00burg%20OR%20beitragezurgesch00will%20OR%20briefevonwilhelm00humb%20OR%20catalogofcourses19561957brig%20OR%20catalogofcourses19571958brig%20OR%20catalogofcourses19581959brig%20OR%20catalogofcourses19591960brig%20OR%20catalogofcourses19601961brig%20OR%20catalogofcourses19611962brig%20OR%20catalogofcourses19621964brig%20OR%20catalogofcourses19641966brig%20OR%20catalogofcourses19661968brig%20OR%20catalogofcourses19681970brig%20OR%20catalogofcourses19701972brig%20OR%20cataloguenumber19321933brig%20OR%20cataloguenumber193233193435brig%20OR%20cataloguenumber19331934brig%20OR%20cataloguenumber19341935brig%20OR%20cataloguenumber19351936brig%20OR%20cataloguenumber193537brig%20OR%20cataloguenumber19361937brig%20OR%20cataloguenumber19371938brig%20OR%20cataloguenumber19381939brig%20OR%20cataloguenumber19391940brig%20OR%20cataloguenumber19401941brig%20OR%20cataloguesannoun19011902brig%20OR%20cataloguesannoun19021903brig%20OR%20cataloguesannoun19031904brig%20OR%20cataloguesannoun19041905brig%20OR%20cataloguesannoun19051906brig%20OR%20cataloguesannoun19061907brig%20OR%20cataloguesannoun19071908brig%20OR%20cataloguesannoun19081909brig%20OR%20cataloguesannoun19091910brig%20OR%20charlotteackerma00ml%20OR%20classschedule19341935brig%20OR%20classschedule19381939brig%20OR%20classschedule19421943brig%20OR%20classschedule19431944brig%20OR%20classschedule19441945brig%20OR%20classschedule19461947brig%20OR%20classschedule19521953brig%20OR%20classschedule19621963brig%20OR%20coeurlegercomedi00daub%20OR%20dasfunfzigjahrig00wien%20OR%20debordeauxversal00rang%20OR%20delagloireetdusa00abla%20OR%20deraufenthaltdes00somm%20OR%20derfeldzugvon18000heil%20OR%20derfriedensvertr00berl%20OR%20dergrazerschloss00velt%20OR%20dertugendbundinb00domb%20OR%20diefunfundzwanzi00robo%20OR%20diekorruptionins00slsn%20OR%20dienapoleonische00blei%20OR%20dieschuldigenein00kunz%20OR%20englandimjahrzeh00schm%20OR%20erinnerungeneinb00sche%20OR%20evangelischegnad00holl%20OR%20fortunaroman00kiel%20OR%20frischhansteilli00lieb%20OR%20gedrangtesjourna00velt%20OR%20gen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