I did a research on all the previous monthly Dragons and here are the results:
Code:
Skeleking Dragon/Skelequeen Dragon: Tuesday, October 3 2017 - Friday, November 3 2017 (31 days in total)
Solar Fyre Dragon/Lunar Fyre Dragon: Friday, November 3 2017 - Tuesday, November 28 2017 (25 days in total)
Old Klaws Dragon/Mama Klaws Dragon: Tuesday, November 28 2017 - Friday, December 29 2017 (31 days in total)
Father Sky Dragon/Mother Earth Dragon: Friday, January 5 2018 - Friday, February 2 2018 (28 days in total)
Beloved Dragon/Forever Dragon: Friday, February 2 2018 - Friday, March 2 2018 [extended up to Monday, March 5 2018 (28 + 3 = 31 days in total)]
Orbit Dragon/Universe Dragon: Friday, March 2 2018 - Friday, March 30 2018 (28 days in total)
So, the norm goes as follows:
One month the breeding items are dropping for 31 days and the next month the breeding items are dropping for 28 days with only one exception so far, on Lunar Fyre Dragon that lasted 25 days instead of 28 days.
According to that schedule it seems that, unfortunately, the White Stars were correclty expired on March the 30th.
Judging by the above norm the Neo Kitsune Dragon/Neo Unicorn Dragon have to last up to Tuesday, May 1 2018 (31 days in total).
So, even though that I am very frustrated, because the norm wasn't clear so far and I lost the Universe Dragon for a few White Stars only, I posted my results as a proof for the next monthly Dragons, hoping that they will don't change this established norm in the future without any notice at all.