Septennialy or Septennially: How To spell?
The word Septennialy is misspelled against Septennially, an adverb meaning "Once in seven years."
Septennially has double "ll" is mispronounced as "l"Remember double 'LL' in between the strings septennia & y which should not be misspelled with single 'L'
Wrong Spelling:  septennia-l-y  Correct Spelling:  septennia-ll-y 
Find more wrongly spelled words of Septennially to spell it well.