平成11年 (Heisei 11) is 1999 in the Western calendar. Check the age and zodiac below.
Yes. Heisei 11 (平成11年 in Japanese) corresponds to 1999 in the Western calendar.
1999 is the Year of the Rabbit (卯(う) in Japanese) in the 12-year zodiac cycle. In the older 60-year sexagenary cycle (kanshi) it is 己卯.
It depends on whether they have had their birthday yet this year. The box near the top of this page calculates both possible ages automatically from today's date — the lower number is their age before their birthday, the higher number is their age after.
Heisei 11 is written 平成11年 in Japanese. It is also commonly abbreviated H11 — for example on driver's licenses and other government forms.