Following the DokuWiki development mailing list, I saw the following changelog:

Sun Apr  6 19:47:18 CEST 2008  Andreas Gohr 
  * work around strftime character limit on parsing namespace templates FS#1366

I checked on the PHP documentation page (by the way, a quick tip: you can access the documentation for a given PHP function by appending the name of the function to the php.net url, for example http://php.net/strftime) and sure enough if says: "Maximum length of this parameter is 1023 characters".