Limitations in IDT when using BW as data source

Hi Experts,

Could anyone please let me know what are the limitations in IDT when using BW as data source.

Because my query is taking much time when I build logic on date field, when I fetch the data by giving particular range on date like "[date] Between '01-06-2015' to '30-06-2015' ", I am getting the data with in seconds.

But when I use predefined condition on date like Month([Date])=Month(CurDate()) And Year([Date])=Year(Curdate()) it is taking huge time to get the data.

Could any one help on this.

I can provide more details if any.

Thanks,

G Sampath Kumar