this is a simple problem
let us say you place the data in columns A thru E, starting with row 1
you want to convert the 1 day data to 2 day, so enter the following:
in cell F1, you type =B1
in cell G1, you type =MAX(C1,C2)
in cell H1, you type =MIN(D1,D2)
in cell I1, you type...