Welcome to the celebration of a month not many people know about!
First off, National Deaf History Month is not a month of the calendar year. Instead, it is the month between March 13th and April 15th, which commemorates several important milestones in American Deaf History.
This is separate from the international sign celebrations. In fact, the UN has chosen September 23rd, 2018 to be the first International Day of Sign Languages. Most countries celebrate Deaf Awareness month or International Week of the Deaf in September. In some areas, December is also an important month because of the birthdays of Laurent Clerc and Thomas Hopkins Gallaudet.