Hi guys, just a quick preliminary calendar for those looking to summon.
It is subject to potential changes, but at least Atlantis seems to be very accurate. Colors were included in case you are looking for the best period to bolster your bench in one specific color.
As costumes are fairly recent we cannot estimate a pattern, but next month should be between Elena, Quintus, Lianna and Vivica.
By the way, do not forget that the % of getting a 5* is low, so it may be wise to summon considering that and aiming for powerful 4* (taking about intermediate players or C2P). I particularly suggest costumes as they have great stats, are more versatile for trial quests and have a higher % of getting a good hero (2.5% versus 1% in events as example, as the other 1.5% is for S1 five stars but uncostumed, so way less powerful).
Good luck to all!