Sybase IQ datepart function strange behaviour

Question

I am facing an issue in Sybase IQ running datepart function which is supposed to return the value of 1 for 2024-01-28, but it returns 7 instead. My char_date column is stored as varchar(10) in the database.

Here are two queries to compare. When I run it on real table data, it returns 7 for the column datep, however for constant varchar(10), it returns the right value (1):

-- 1
SELECT char_date , datepart(dw,  cast(char_date AS date)) as datep
FROM MyTable

-- 2
SELECT '20240128' char_date , datepart(dw,  cast('20240128' AS date)) as datep

Output: