15 Versus 十五

[Kisshu]

I have a question here. In what situations would you use numbers and in what situations would you use kanji? Does is really matter? Would it be correct to say this sentance both ways?

私は１５歳です。

私は曙ﾜ歳です。

Can anyone give me examples of situations in which only one of these could be used?

[richvh]

It's customary to only write Christian era dates in Arabic numerals. Other than that, I'm not aware of any rules, though it is common to write numbers in Arabic numerals since they are more compact that way.

[keatonatron]

It doesn't really matter. Arabic numerals are more common, kanji are seen in more "polite" places like newspapers and official documents.

[two_heads_talking]

I would have to say as long as you are consistant.. either kanji or roman numberals but not a mix. as keatonatron says above.. media sources and official documents use kanji more often than not..