"Anniversary" comes from Latin: "anni" [genitive of annus = year] + "vers(us)" [past participle of vertere = to turn]. I am interested in constructing a similar word which means "reoccurring every 1000 days".

"One thousand", in Latin, is mille and the genitive plural of "day" is dierum. Hence: mille-dierum-versary. However, this doesn't sound brilliant -- I know very little about Latin, so am not sure how its affixation works -- so does anyone have any better suggestions?

  • 3
    How about just milleversary? Commented Oct 3, 2013 at 16:07
  • 6
    You could just call it a 'thousand-day anniversary', and people won't bat an eye. It may not be technically correct, but your meaning will be understood. Better understood than creating a word based on the two that would take some interpreting and could mislead someone into thinking you mean something entirely different.
    – Zibbobz
    Commented Oct 3, 2013 at 16:08
  • How about milledierum celebration?
    – Talia Ford
    Commented Oct 3, 2013 at 16:57
  • 1
    There is no reason not to use the word 'anniversary'. Merriam-Webster gives "broadly : a date that follows such an event by a specified period of time measured in units other than years the 6-month anniversary of the accident" in sense 1 for anniversary
    – nohat
    Commented Oct 1, 2019 at 3:03
  • 1,000th-day anniversary.
    – Lambie
    Commented Feb 3, 2020 at 20:07

5 Answers 5


The Urban Dictionary lists an obvious choice: kiloversary, also known as k-day.

(Coming soon to a Hallmark card near you.)

  • I'm quite liking "k-day": I think I'll go with that :) Commented Oct 3, 2013 at 22:08
  • If it's celebrating 1,000 days of some bacteria surviving in a petri dish, Kiloversary sounds alright, but if you're celebrating 1,000 days together with a loved one, milleversary sounds so much better. Mille is the French word for thousand and comes from Latin whereas kilo- comes from greek and sounds far more technical and scientific... Same for 100, btw. I'd take centennial over hectonnial ( from the Greek hekaton for 100 )
    – OneProton
    Commented Feb 3, 2020 at 19:01

I would use 1,000 day commemoration to celebrate something that is not in years.


In Italian it is "millesimo giorno".


It should be "thousandth day".

"That tradition is celebrating its thousandth day"


  • 1
    OP was looking for a word to mean thousandth day anniversary not for a repetition of the question. Although the Italian link was interesting, so no downvote. :)
    – OneProton
    Commented Feb 3, 2020 at 19:08


Because M = Roman numeral for 1000

  • I don't know why this post was downvotes. M of course stands for Mille (thousand), and it's a pretty good answer, especially considering we call 1,000 years a millenium and use M on monuments to signify the a point in time: MCMXVIII anyone?
    – OneProton
    Commented Feb 3, 2020 at 19:04


Although I don't think a word exists in common usage I wouldn't hesitate to use Milleversary.

While The Greek root work kilo- could be used, when it comes to the passage of time, Latin root words are more commonly used.

Mille is the latin word ( and French and Italian spelling ) for 1,000. and we use it with the other popular time-related word: Millennium. We also use the Latin centum for 100 (in century and centennial) rather than the Greek hekaton.

By way of contrast, we use the greek prefixes kilo- and hecto- often in weights and measures.

  • A hectare is 100m x 100m
  • Kilogram, kilometre, kilopascal

Additionally, we often use Roman numerals to signify or demarcate points in time. M means 1,000 in Roman numerals. You see MCMXVIII all over Europe on monuments erected referring to WWI, like the Welsh National War Memorial which has on it MCMXIV–MCMXVIII on its outer frieze.

You used to see Copyright marks all the time using roman numberals as well, like ©MCMLXXIV (before 2000 mostly, as ©MMI is a little odd-looking I'd imagine).

French still extensively uses Roman numerals to refer to centuries. Xe is often used to mean the 10th century or dixième siècle.

The very passage of time on a clock is STILL very often marked in roman numerals, from I to XII. For these reasons, I'd definitely say milleversary sounds more natural than something like kiloversary if it's anything beyond measuring how many days a bacterial strain has survived inside a petri dish.

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