SQL select works in Management Studio, but not from website - sql-server

Question

I have the following query:
SELECT
[tblstudentrakazot].studentid, firstname, lastname, tblRakezetSchedule.*
FROM
tblRakezetSchedule
INNER JOIN
[tblstudentrakazot] ON [tblstudentrakazot].scheduleID = tblRakezetSchedule.scheduleid
INNER JOIN
tblstudents ON [tblstudentrakazot].studentid = tblstudents.studentid
WHERE
scheduleday = datepart(w,convert(datetime,'21/2/2016',103))
AND tblRakezetSchedule.rakezetID = 182
ORDER BY
replace(scheduletimefrom, ':', '')
When run from SQL Server Management Studio, it works perfectly and generates 3 records.
When run from my VBscript app, I get no records
The issue seems to be in the filter that refers to the date scheduleday = datepart(w,convert(datetime,'21/2/2016',103)) - when I comment that out, the query works.
Does anyone know what the issue can be?
I have tried playing with the date settings but that didnt change anything.
I have tried doing CONVERT(int,scheduleday) in the WHERE - that didn't help either, as the scheduleday is already a number format field.
I have tried using dw in the datepart instead of w - also no change.
Thanks in advance
UPDATE:
The query works when I do WHERE CONVERT(int,scheduleday) = 1
Also - I see that CONVERT(int,datepart(w,convert(datetime,'21/02/2016',103))) correctly gives 1 too. Its just weird that 1 <> 1 even when they are both converted to INT
Here is my VBscript:
sql = "SELECT [tblstudentrakazot].studentid, firstname, lastname, tblRakezetSchedule.* FROM tblRakezetSchedule"
sql = sql & " INNER join [tblstudentrakazot] on [tblstudentrakazot].scheduleID = tblRakezetSchedule.scheduleid "
sql = sql & " INNER join tblstudents on [tblstudentrakazot].studentid = tblstudents.studentid"
sql = sql & " WHERE "
sql = sql & " CONVERT(int,scheduleday) = datepart(w,convert(datetime,'" & cleanSQL(planneddate) & "',103)) AND "
sql = sql & " tblRakezetSchedule.rakezetID = " & CleanSQL(x_rakezetID)
sql = sql & " ORDER BY replace(scheduletimefrom, ':', '')"
WHERE:
x_rakezetID = 182
and planneddate is a date variable in the format of `21/02/2016'

Answer 1

The result of SELECT datepart(w,convert(datetime,'21/2/2016',103)) will depend on your session's language settings (which will depend on the user.) For example:
SET LANGUAGE German;
SELECT datepart(w,convert(datetime,'21/2/2016',103)) ;
...returns 7, whereas for English it returns 1.
I therefore suspect that you are using different users or at least different language settings when connection through SSMS versus through your application.