There is a Daniel Gilman b. 1800 to Daniel and Sarah Richardson Gilman, don't know if it's the same man.
New Hampshire Birth Records, Early to 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:FLP2-QZD), Daniel Gilman, 25 May 1800; citing Belmont, Belknap, New Hampshire, United States, Bureau of Vital Records and Health Statistics, Concord; FHL microfilm 1,000,944.
Name Daniel Gilman
Birth 25 May 1800 Belmont, Belknap, New Hampshire
Father Daniel Gilman
Mother Sarah
New Hampshire Marriage Records, 1637-1947," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:FL6F-PDX), Daniel Gilman and Sarah Richardson, 16 Jun 1788; citing , Bureau of Vital Records and Health Statistics, Concord; FHL microfilm 1,000,996
Name Daniel Gilman
Marriage 16 Jun 1788
Spouse Sarah Richardson
Clerk's Jurisdiction Belmont, Belknap, New Hampshire