Why does this return '2015-01-19'?:

```
SELECT date
FROM hours 
HAVING date BETWEEN DATE_SUB(max(date), INTERVAL 2 DAY) AND DATE_ADD(max(date), INTERVAL 1 DAY)

```

when this returns '2015-01-20' and '2015-01-19'?:

```
SELECT date 
FROM hours 
HAVING date BETWEEN '2015-01-18' AND '2015-01-21'

```

max date is '2015-01-20' and there are records on both '2015-01-20' and '2015-01-19'. date is a date field.