In English 1987 can be said nineteen eighty seven and everyone understands what you mean.

If one said deknaŭ okdek sep would it be understandable and acceptable usage?

I think that form would be confusing for speakers of other languages. If someone said to me "Mi skribis ĝin en dek naŭ okdek sep" ("I wrote it in 1987"), I would first assume that dek naŭ okdek sep was the name of the font used.

A Swedish or German komencanto might come up with "dek naŭ cent okdek sep" instead (nittonhundraåttiosju = nineteen hundred eighty seven).

Bemused:If one said deknaŭ okdek sep would it be understandable and acceptable usage?

It would be confusing even to a native English speaker. Dates simply aren't said that way in Esperanto, so even a native English speaker (like me) would automatically assume you were talking about something other than a date.

I would probably figure it out if you spoke a very 'beginner' Esperanto, full of errors; I would gather that you were translating too literally from English. If you had otherwise perfect grammar and accent, though, I'd be mystified.

As another numerical note, it was relatively late in my Esperanto 'career' that I learned that house numbers are read out as normal numbers in Esperanto; so if you live at 39201 Main Street, that wouldn't be read in Esperanto as tri-naŭ-du-nul-unu, that would be read as tridek naŭ mil ducent unu.

If you think about it, building numbers are irregular in English. If it's a short number like 52 we say it as fifty two, but for a long number we tend to read out the digits.

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As a sidenote, you would probably be confused for at least a moment or so if someone said that something happened in "one thousand, nine hundred, and eighty five", particularly if it came in a native English accent. If it were a foreigner whose English was otherwise imperfect, you might guess more quickly that this foreigner doesn't understand how we pronounce dates in English.

mil naŭcent okdek sep - 6 syllables
"nineteen eighty-seven" - 6 syllables

This is why there is no real need for such a shorthand form.

I add the year in the sentence. I am used to the Chinese and Malay way of telling the time and date.

Hope this is not wrong.

EoMy:I add the year in the sentence. I am used to the Chinese and Malay way of telling the time and date.

Hope this is not wrong.

If you mean you are adding the word "jaro" in your sentences, that's perfectly OK: "Mi skribis ĝin en la jaro du mil dek unu."

Some people use ordinal numbers: "en la mil naŭcent naŭdek oka (jaro)". This is not wrong, just uncommon.

Bemused:..1987..If one said deknaŭ okdek sep would it be understandable and acceptable usage?

I might use okdek sep as a short form myself.