Does "curtain time" means "on show time"?

Solution 1:

1)

The Japanese-English dictionary, it says "curtain time" means the time that show starts. But I seldom see this phrase on actual posters or tickets.

Curtain time does indeed mean the time the show starts, it's a phrase seldom used, which is why you do not see it in popular advertisements.

Curtain time

The beginning of a stage performance. ‘curtain time is at 8 p.m.’ - OLD.

It's more typically associated with theatre than music.

2)

I am now writing a Japanese to English translation about an upcoming music concert. Is it correct to write "Doors open XX P.M. Curtain Time XX P.M." or any other better choices?

If your music concert is operatic, you could use curtain time, but if the music concert is popular music, this would sound too formal.

For a less formal alternative you could use:

Doors open XX P.M. Concert starts XX P.M.

or

Doors open XX P.M. Music starts XX P.M.

or, as @HotLicks mentioned below:

Doors open XX P.M. Performance starts XX P.M.

Solution 2:

In theatrical circles, we speak of both 'curtain up' and 'curtain down' times. The colloquial expression might be 'what time does the show go up?' or 'what time does it come down?' 'Curtain up at 8.00, curtain down at 10.00'. But the curtain is rarely mentioned in advertising etc. It would more likely be 'Monday at 8.00, doors open 7.30'.