Epic Deific diadem: how sacred bonus works?

[Fanaval]

Greetings,

I ask devs to clarify if, using the item Epic deific diadem, the sentence "On spell cast: +1 sacred bonus to the DC of that school" means that the +1 sacred bonus is applied when the spell is casted and before it lands on target (so, for example every time I cast a finger of death spell I have a +1 on necromancy on that finger of death before the spell lands) or if the +1 sacred bonus is applied after the spell lands on target (so, for example, every time I cast a finger of death I have a +1 sacred bonus on the NEXT necromancy spell I will cast).

Thanks.

[Fanaval]

Is it possible that the devs don't know a simple answer to this question?
Thanks.

Greetings,

I ask devs to clarify if, using the item Epic deific diadem, the sentence "On spell cast: +1 sacred bonus to the DC of that school" means that the +1 sacred bonus is applied when the spell is casted and before it lands on target (so, for example every time I cast a finger of death spell I have a +1 on necromancy on that finger of death before the spell lands) or if the +1 sacred bonus is applied after the spell lands on target (so, for example, every time I cast a finger of death I have a +1 sacred bonus on the NEXT necromancy spell I will cast).

Thanks.