Women's History Month:
In 1981, the U.S. Congress passed a resolution establishing National Women’s History Week. The week was chosen to coincide with International Women’s Day, March 8. In 1987, Congress expanded the week to a month. Every year since, Congress has passed a resolution for Women’s History Month, and the U.S. president has issued a proclamation.
I found the above on the women, so it would appear that Women's History Month is not actually on the statute books.
EDIT: I have now found the pertinent Presidential proclamations for Women's History month and Black History Month.
Black History MonthWomen's History MonthThe bill is thus unnecessary unless a President were to revive the practice of making these proclamations.