If John served in the Revolution, he had to have been born earlier than 1768 (the war lasted 1775-83).

The even spacing of the birth years supplied by Rucker (see below) suggests they are estimates, which is supported by the fact that the known birth years are different.

1.  Marriage Record:

2.  1790

3.  1800

4.  1810

5.  1820

6.  1830

7.  1840

8.  1850

9.  1860 Census Every-Name-Index/Images (online at Ancestry.com, Image #58 of 149):  Spring Hill Forge P.O., Lincoln Co., NC, Roll M653_904, p. 103B, PN 74, 504/485, enumerated 13 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Philip Hovis	52	M		Farmer	1200	3335	North Carolina
[Philip's wife and children]
Elizabeth "	70	F					"

10.  Elizabeth Hoyle Rucker.  c1938.  The Genealogy of Peiter Heyl and His Descendants, 1110-1936...  Zolliecoffer Jenks Thompson et al., Shelby, NC (online at HeritageQuest at Genealogy.com):

p. 50

REV. JOHN HOVIS (5) b. 1768, m. about 1790, Sarah Katherine Rhyne, dau. of Jacob Rhyne, pioneer.  They lived on Hoyl's Creek, a little northeast of old Harden Station, a part of the old Rhyne homestead.  John Hovis fought in the Revolutionary War; he was a member of Capt. James Houston's Company, and fought in the battle of Ramsour's Mill.  (See Hunter's Sketches, Page 196.) His children:   Jacob Hovis.......  250 ...  b  1791. Elizabeth Hovis...  251 ...  b 1793. Sarah Hovis.......  252 ...  b 1795. Mary Hovis........  253 ...  b 1797. Susannah Hovis....  254 ...  b 1799. David Hovis.......  255 ...  b 1801. Solomon Hovis.....  256 ...  b 1803. Philip Hovis......  257 ...  b 1805. George Hovis......  258 ...  b 1807.

As a source, Rucker has been demonstrated over and over that she was guessing wildly at dates.

11.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).