Ten twelve is fine. It can also be stated as "twelve after ten", but that would sound a little formal. By the way, use colons instead of periods (10:12).

Yes it is correct Aliona!

Lance Gough's response is correct only for American English. The way you have written the time is fine. The 'dot' after the ten is correct and quite common outside N. America. It is also unusual to say "twelve after ten" outside N. America. I'd say either "ten twelve" or "twelve minutes past ten". Both of these sound precise, but not especially formal.