Filtering by Day and Month hidden

[+CheekyBrit]

OK, for all you stat freaks like me, I'm trying to find the best way to filter based on hidden month and day of the calendar, but not limiting it to year.

Why?
There's a lot of challenges based on filling the hidden date calendar with a specific type / size / attribute. Or perhaps a challenge to find all sizes/types/difficulties/terrains... hidden on one day or one month.

Some examples are:
GCA3VD4 Busy hidden day - all 7 sizes challenge

GCAHP8B Leap Day hidden challenge

GC9XA74 Gridbusters: Hidden month / found month challenge

GC6JV7B Gridrunner Challenge: One Date Placed Starbar

GC6JV7D Gridrunner Challenge: Placed Grid Dim Starbar

How can we filter this?
The best options I have found so far are:

- On geocaching.com change the "placed date" as "on" the specific day for each and every year the game has existed. That's only 24 separate searches but it is a bit tiresome.
- On GSAK (Geocaching Swiss Army Knife) use the 'get geocaches' feature to grab local caches up to 100 miles radius, then use the DayMonthFilter.gsk macro and pick the hidden day of choice. With this option you have to have lots of different databases each covering a circle of up to 100 miles radius in order to search a wide area.
- There is some SQL you can do on GSAK for a similar effect but it is also limited by the database you're working in only having caches from a 100 miles radius.
- C:Geo the android app has better filtering options but functions the same as geocaching.com - you need to repeat for each individual day, month, and year. There's a named filter option but that doesn't seem to allow open year, specific day and month.

- Project-gc.com has the 'date hidden tool' but it only works if your calendar has gap(s) for exactly which days you want to search. They have custom filters but day and month hidden are not among the options.
- Cachly might hold the key, but I don't have an iphone and am unfamiliar.

Anyone have any better solutions? Please mention them here.

[+CheekyBrit]

58 minutes ago, HHL said:

That's wrong. GSAK is not limited to grab geocaches up to 100 miles.

That's FANTASTIC!!!!! I'm excited to try this out. 
My false information comes from this error message that came as I tried a circle with a radius of larger than 100. I'll have another go reading that help file to see how it works.