ok.. this was bothering me for a while
what you need is the following
1) A cell with today's date with the same formatting as the dates you place on each flight record - For this I will refer to this as cell C1
For the cell to display the last say 28 days of hours use the following
=SUMIF(B1:B20,">="&C1-28, A1:A20)
where A1:A20 are 20 of the flight log hours - P1 in your logbook thingy
B1:B20 are 20 of the flight log dates
so to change it for the 90 just change to
=SUMIF(B1:B20,">="&C1-90, A1:A20)
and 365
=SUMIF(B1:B20,">="&C1-365, A1:A20)
In english the formula is
Add up all the flight hours for each flight record which is newer than today less XX days
let me know if that works
I've tested in on Open Office Calc but it should do for excel