The Apology Day/Weekend is a spontaneous event set up as compensation for a rollback or any system/server related failures. During the event, IAP (In-App Purchases) will give you 25% more gems, and all players have a chance of getting a lucky drop when breaking blocks. These lucky drops are indicated by a small red flash, and they give the item itself, it's seeds, and a gem drop of a higher value than what one would usually get from the block. This bonus only applies to blocks which normally drop gems and seeds. It also gives Lucky! Mod to all players until the end of the day.
In addition, a special item is usually available during these events to commemorate the work lost to the rollback prior. The Rollback Plaque, Rollback Plaque II, and Rollback Plaque III were available for the first, second, and third Apology Weekends/Day respectively.
Three Apology Weekends/Day have been issued thus far: one for the weekend of February 23rd in 2013, one for the weekend of October 5th, 2013, and one for the weekend of August 10th in 2015.