For the last couple years, the exponential sum of the day for Easter Sunday has been a cross.
This was not planned, since the image each day is determined by the numbers that make up the date, as explained here.
This was the exponential sum for last Easter last year, April 1, 2018:and this was the sum for this Easter, today, April 21, 2019:A partial explanation is that Easter usually falls in April, the fourth month, and the sums for April often have four-fold symmetry.
That said, many of the images in April look nothing like a cross.
And in fact the image for next Easter, April 12, 2020, will be an asymmetric mess.