Boy, there is a huge difference in performance between Date::Manip::Date and Time::Piece ...

[user@host newload]$ ./t-benchdates.pl 500
Benchmark: timing 500 iterations of Date::Manip::Date, Time::Piece...
Date::Manip::Date: 124 wallclock secs (119.35 usr +  1.30 sys = 120.65
+ CPU) @  4.14/s (n=500)
Time::Piece:  5 wallclock secs ( 3.88 usr +  0.03 sys =  3.91 CPU) @ 1
+27.88/s (n=500)
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Certainly a code change I will be making but that leaves the foreach loop through all available ranges as a massive performance hit still ...