Performance troubles

I'm using sql server 7 with asp. The database the script is searching contains around 5000 records.

There is a real time difference between these two queries:

SELECT * FROM classicalconcerts where vetted = 'Yes' and performancedate >= '30/05/01' and performancedate <= '30/05/01' and publishdate <= '30/05/01' order by performancedate, country, county, city, venueid asc

(returns 15 results)

and

SELECT * FROM classicalconcerts where vetted = 'Yes' and performancedate >= '30/05/00' and performancedate <= '30/05/02' and publishdate <= '30/05/01' order by performancedate, country, county, city, venueid asc

(returns 4000 results)

The only difference is the date span.

The code for returning the records is as follows:

Set oRs = Server.CreateObject("ADODB.Recordset")
     oRs.ActiveConnection = conn
     ors.CursorLocation = adUseClient
     oRs.Open(SQL)
     
     if ors.EOF then
     call NoRecordsFound
     end if
     
     ors.movefirst
     oRs.cachesize=mypagesize
     howmanyrecs=oRs.recordcount
     numbrecs = howmanyrecs
     oRs.pagesize=mypagesize
     maxcount=cint(oRs.pagecount)
     oRs.absolutepage=mypage
     allconcertdata = ors.getrows
     ors.Close
     set ors = nothing

The script then displays the first 15 records on the page and a 'next' button.

The time difference is about 30 seconds and I can't work out why there should be a difference. Any ideas?

Thanks.