Breakdown of Этот период длился с две тысячи пятого до две тысячи пятнадцатого года.
этот
this [f: эта, n: это]
два
two
год
year
тысяча
thousand
Questions & Answers about Этот период длился с две тысячи пятого до две тысячи пятнадцатого года.
Why do we say две тысячи пятого instead of changing all the words to the Genitive case?
In Russian, years are read as ordinal numbers, similar to saying the two thousand and fifth year. For compound ordinal numbers, only the very last word changes case. The preposition с requires the Genitive case, so две тысячи stays in its base form, and only пятый changes to пятого.
Why does the word года only appear at the end of the sentence?
When expressing a continuous range of years, you do not need to repeat the word for year. You state the first year's number, then the second year's number, and place года (the Genitive form of год) at the very end of the phrase.
Could I use the preposition по instead of до for the end of the date range?
Yes, but the grammar changes. The combination с ... до ... uses the Genitive case for both years. If you use с ... по ... (which strongly emphasizes up to and including), the second year must be in the Accusative case, so you would say по две тысячи пятнадцатый год.
Why does the verb длился (lasted) have a reflexive -ся ending?