Hi Dink,
I am thinking your talking about REG E timeframes? The FI has 10 Business days to resolve a claim of error, if they cannot do so they must provide Provisional Credit, then they have an additional 45-90 Calendar days to provide resolution. From my POV: Business days allow the bank a more reasonable time frame to RESOLVE a claim, which is in the Consumers Best Interest.The calendar days & Business days start ticking from the date the claim is taken, so the 10& the 45/90 run along side one another.
You might be able to find a commentary on REG E to better explain why legally the time frames where set up they way they where.