Dataview: <=date() not working?

I have some dataview code in my weekly review template designed to return results from a given week. It looks like this:

table dinnerlog as "Log"  
where dinnerlog != null AND 
file.day >=date({{monday:YYYY-MM-DD}}) AND file.day <=date({{sunday:YYYY-MM-DD}})
sort file.name asc

When the template is applied, the dates are filled in correctly. However! The results include entries from Mondays, but not entries from Sundays. If I manually change the second date so that the “<=date()” is the following monday, it does return entries from Sunday. It’s as though I’m just using a < operator instead of <=.

I’m confused as to why the = part of the equation seems to work for the beginning of the week, but not the end.