-is NULL, the associated time
-information will not be returned or set.
+is non-NULL,
+.Fn gettimeofday
+will populate the timezone struct in
+.Fa tzp .
+If
+.Fa tp
+is non-NULL and
+.Fa tzp
+is NULL, then only the timeval struct in
+.Fa tp
+is populated. If both
+.Fa tp
+and
+.Fa tzp
+are NULL, nothing is returned.