表语从句与定语从句的转换：when=the day when？

下面句子中的when…是引导定语从句，修饰the day：
Sunday is the day when very few people go to work.
上面的句子能不能省略the day，使when…变成一个表语从句呢？如：
Sunday is when very few people go to work. 星期日是没什么人上班的日子。