It is/was incorporated on 1 Jan 1991.

[Winwin2011]

ABC company is listed on the stock market. Which of the following sentences is correct?

1. It was incorporated on 1 Jan 1991.
2. It is incorporated on 1 Jan 1991.

 

[MikeNewYork]

The first is better. In AmE we would write it as "on January 1, 1991". It should be "was" because it happened in the past.