Hi,
Modify your table to look like this:
AA_____AB
0______0-30
31_____31-60
61_____61-120
121____121-180
181____181-240
241____241-300
301____301-365
365____365+

If this table is in AA1:AA8, then:
=VLOOKUP(D2,$AA$1:$AA$8,2)

Regards - Dave.