I am trying to calculate days between two dates so that I can find out if they fall in the 30 / 60 / 90 day bracket

The calculation I am using is working fine

`DATEDIFF(day, dbo.TblReturnDetails.RcvdDate, { fn NOW() })`

what I am trying to do now is say

if the days is less than 90 then give a number 3

if the days is less than 60 then give a nmber 2

if the days is less than 30 then give a number 1

`CASE WHEN DATEDIFF(day , dbo.TblReturnDetails.RcvdDate , { fn NOW() }) >= 90 THEN '3' WHEN DATEDIFF(day , dbo.TblReturnDetails.RcvdDate , { fn NOW() }) >= 60 THEN '2' WHEN DATEDIFF(day , dbo.TblReturnDetails.RcvdDate , { fn NOW() }) >= 30 THEN '1' END`

but at the moment using the above Case I get the following data.

```
Day
199 3
55 1
29 NULL
17 NULL
17 NULL
```

can anyone see where i am going wrong?