MarathonG 15

Marathon G15:
Log in each day of an entire month and complete at least one Daily Challenge

This achievement requires that you complete a single Daily Challenge for each day in an entire month. The description is a bit misleading. You only need to complete a puzzle from each day. You DO NOT have to actually log in each day to earn this achievement. For example, in August, you can unlock this achievement by only logging in on August 31st and completing a single challenge from each of the 31 days in the month. Also, as long as you are in the current month, you can advance your computer's settings head to the last day of the month to have access to all of the challenges.

This will unlock on the way to getting the "Perfection" achievement.