The Collaborative International Dictionary of English v.0.48:

Daysman \Days"man\ (d[=a]z"m[a^]n), n. [From day in the sense of
   day fixed for trial.]
   An umpire or arbiter; a mediator.
   [1913 Webster]

         Neither is there any daysman betwixt us. --Job ix. 33.
   [1913 Webster]

Easton's 1897 Bible Dictionary:

Daysman
   an umpire or arbiter or judge (Job 9:33). This word is formed
   from the Latin diem dicere, i.e., to fix a day for hearing a
   cause. Such an one is empowered by mutual consent to decide the
   cause, and to "lay his hand", i.e., to impose his authority, on
   both, and enforce his sentence.