Some sources give the opening date as April 14, 1975, but other sources, including The Best Plays of 1974-1975, give April 17 as the opening date. The production itself announced April 14 as the opening date, but it was requested that reviews not be published till April 18. It seems that some critics were not invited till after April 14. We are choosing to go with April 17 as the opening date.
In addition, some sources incorrectly give a performance total of 80. This is simply wrong. The production played seven performances a week, not eight. It played 67 performances from April 17 till it closed on June 21. If counting from the April 14, the total would be 70, but it did not play 80 performances no matter what date is counted as the opening.