MarathonG 40

This can be done by changing the system clock. For obvious reasons, your best course of action is to use February as your month to complete this achievement. Set your system clock to February 1st, open Mahjong, complete one challenge (I recommend an easy score attack or easy match attack, as these were the fastest for me), collect your coins, and close the program. Change the system clock to February 2nd, and repeat for each day through the 28th. While it might not be necessary to close the program out each day, I recommend doing this anyway just to be safe. If you are not given the option of an easy score/match attack game, use your judgement. You should always get at least 1 easy puzzle. For me, medium and sometimes even hard score/match attack challenges were quicker than easy variants of the other game types (but never expert; expert score/match attacks always took me at least 4-5 tries). My personal experience was that score/match attack games were the fastest, followed by golden tiles, followed by lightning tiles, followed by classic games.

Once you have completed the 28th challenge, the achievement should unlock. Since you will now be set to Feb. 28, you can now go back and do all of the challenges for the entire month for your "Strive For Perfection" achievement. Your "Diamonds are Forever" achievement will unlock along the way, and you will be one medal closer to your "Go for the Gold/Silver/Bronze" achievements.