The error that I am getting is :

Ambiguous date/datetime constant. Use the format:
{^yyy-mm-dd[,]hh:[mm:[ss]]a/p]]}

I've tried formatting the date exactly like that and every which way possible and I'm still getting the exact same error. The startdate field is a date[8] type in the table. I thought that maybe the BETWEEN() function would only work with a datetime field, but it worked for me once before. Now I'm trying everything and it's not working. I also tried changing the format so that it was just

WHERE start_date >= {2000/04/01} AND start_date <= {2001/03/31}

but I still got the same error.

Any further suggestions?