Following are all the octennium like words, in the list below.
DECAMILLENNIUM
100% like octennium
QUINCENTENNIUM
100% like octennium
OCTOCENTENARY
100% like octennium
DUODECADE
100% like octennium
TENS
100% like octennium
EIGHTIES
100% like octennium
ETERNITY
100% like octennium
ZEROES
100% like octennium
MILLIONENNIUM
100% like octennium
TWELVEMONTH
100% like octennium
SEMICENTURY
100% like octennium
HALF-CENTURY
100% like octennium
SEMIDECADE
100% like octennium
SEVENTIES
100% like octennium
TEENS
100% like octennium
SEVENNIGHT
100% like octennium
2080S
100% like octennium
AUTUMNTIME
100% like octennium
NINETIES
100% like octennium
MILLENNIUM
100% like octennium
ZEROIES
100% like octennium
SIXTIES
100% like octennium
MIDEIGHTIES
100% like octennium
SEXENNIAL
100% like octennium
2070S
100% like octennium
2060S
100% like octennium
2090S
100% like octennium
MEGA-ANNUM
100% like octennium
NUNDINE
100% like octennium
1980S
100% like octennium
1780S
100% like octennium
2160S
100% like octennium
2020S
100% like octennium
2040S
100% like octennium
SEMICENTENNIAL
100% like octennium
2010S
100% like octennium
TWO-THOUSANDSIES
100% like octennium
1990S
100% like octennium
TWENTIES
100% like octennium
1710S
100% like octennium
ZEROS
100% like octennium
TWO THOUSANDS
100% like octennium
AUTUMN YEARS
100% like octennium
2000S
100% like octennium
TURN OF THE CENTURY
100% like octennium
MIDSEVENTIES
100% like octennium
TWILIGHT YEARS
100% like octennium
1970S
100% like octennium
1790S
100% like octennium
2050S
100% like octennium
AUTUMN
100% like octennium
NINETEEN HUNDREDS
100% like octennium
1880S
100% like octennium
1720S
100% like octennium
DUODENE
100% like octennium
SENNIGHT
100% like octennium
EPAGOMENA
100% like octennium
EPHEMERON
100% like octennium
FORTIES
100% like octennium
1760S
100% like octennium
MIDYEAR
100% like octennium
1960S
100% like octennium
TENDAY
100% like octennium
1380S
100% like octennium
DéCADI
100% like octennium
FIFTIES
100% like octennium
MIDTEENS
100% like octennium
HALFMONTH
100% like octennium
TWOS
100% like octennium
'10S
100% like octennium
1370S
100% like octennium
2030S
100% like octennium
1860S
100% like octennium
EIGHTISH
100% like octennium
1810S
100% like octennium
110S
100% like octennium
GOLDEN YEARS
100% like octennium
NYCHTHEMERON
100% like octennium
1800S
100% like octennium
1700S
100% like octennium
120S
100% like octennium
FIN DE SIèCLE
100% like octennium
1770S
100% like octennium
HOUR
100% like octennium
MIDSIXTIES
100% like octennium
BIMESTER
100% like octennium
1740S
100% like octennium
CONCURRENT
100% like octennium
1950S
100% like octennium
1750S
100% like octennium
ATOMIC WINTER
100% like octennium
1870S
100% like octennium
1820S
100% like octennium
OPETIDE
100% like octennium
NINE
100% like octennium
TWEENLIGHT
100% like octennium
INTERSTADIAL
100% like octennium
FORETIDE
100% like octennium
SE'NIGHT
100% like octennium
ONE-HUNDRED-YEAR STORM
100% like octennium