For months with 31 days, all 31 days count. For February, the 29th counts. So, if you have not found a cache on Feb 29th before, 2016 is your first opportunity to use February to qualify - if you want to use February as a qualifying month that is.
This is also NOT a 210 day challenge to find caches 210 days in a row.
If you recently started geocaching, on the 1st of a month with 30 days, this is certainly a great way to start the challenge requirements. To complete the challenge, if your statistics are public, just state the months and I'll verify and email if your profile does not show you've met the requirements. Otherwise, post an image showing your find stats.
If you do not currently qualify, simply post a "write note" log with your find and convert to a "found it" log once you satisfy the requirements. Note on the stages: first stage is relatively near a cache placed by Walden Pond - archived long ago, and final stage is not too far from a cache called Johnny Cache. All stages are relatively easy finds, especially in the winter. In the heat of the summer, you may find plenty of obstacles, so seek during the winter even if you do not currently qualify.