positive_mod 44 ext/date/lib/dow.c return 6 - positive_mod(j, 4) * 2; positive_mod 55 ext/date/lib/dow.c y1 = positive_mod(y, 100); positive_mod 57 ext/date/lib/dow.c dow = positive_mod((c1 + y1 + m1 + (y1 / 4) + d), 7);