Why I can not search all records in my fn_dblog

Hi All,

I am currently work with SQL 2008, I want search my transaction log which never truncate before and around sized 1XXGB,

When I doing search, it only show current date records, if I specify yesterday (for example) it return nothing

My Code:

===============

SELECT Operation,[Transaction ID], [Begin Time], [Transaction Name], [Transaction SID]
FROM fn_dblog(NULL, NULL) WHERE [Transaction ID] = ‘0000:00000752’
AND [Operation] = ‘LOP_BEGIN_XACT’ And [Begin Time] = cast(2015-12-02 as date)

===========================Return Nothing, If change today, it return records,

I don't know why, and hope all you can help me

Best Regards,

Calvin