Comparison of tagged units

Consider this data set:

BNikkei = {{10.0032, 27 Days}, {10.0527, 22 Days}, {10.1283, 18 Days}} 

from a recent question, “More effective way to apply a function in one member of a pair ..”

How to get Select[ to work for #[[2]] < 22 Days? I tried:

Select[BNikkei, #[[2]] < (22 Days) &] (* {} *) 

Units in MMA are a great convention. I can’t seem to find too much in manuals, on this situation. Unless, I have to derive comparison functions, for my own types??? Thanks in advance.