It's weird, but since this post I uploaded the website to the clients domain host, and find that the search works perfectly.
I have previously been testing locally using Mamp Server on my Mac.
Locally on my Mac, the search omits the start date.
Remotely on the website, the search is perfect.
The remote server has PHP 5.2.9
MAMP on my Mac has PHP 5.2.6
I will have to check the local configuration and compare with remote, and perhaps download and install the latest version of MAMP
I thank you Dave and Jason for your efforts, and so sorry I have wasted your time.