diff --git a/lib/chkname.c b/lib/chkname.c
index 98f791706..448bc91fb 100644
--- a/lib/chkname.c
+++ b/lib/chkname.c
@@ -33,6 +33,7 @@
 
 #include "defines.h"
 #include "chkname.h"
+#include "string/ctype/strisascii/strisdigit.h"
 #include "string/strcmp/streq.h"
 
 
@@ -69,7 +70,11 @@ is_valid_name(const char *name)
          *
          * Also do not allow fully numeric names or just "." or "..".
          */
-	int numeric;
+
+	if (strisdigit(name)) {
+		errno = EINVAL;
+		return false;
+	}
 
 	if ('\0' == *name ||
 	    ('.' == *name && (('.' == name[1] && '\0' == name[2]) ||
@@ -84,8 +89,6 @@ is_valid_name(const char *name)
 		return false;
 	}
 
-	numeric = isdigit(*name);
-
 	while (!streq(++name, "")) {
 		if (!((*name >= 'a' && *name <= 'z') ||
 		      (*name >= 'A' && *name <= 'Z') ||
@@ -99,12 +102,6 @@ is_valid_name(const char *name)
 			errno = EINVAL;
 			return false;
 		}
-		numeric &= isdigit(*name);
-	}
-
-	if (numeric) {
-		errno = EINVAL;
-		return false;
 	}
 
 	return true;
diff --git a/lib/strtoday.c b/lib/strtoday.c
index 01f2e9b7e..010f12a39 100644
--- a/lib/strtoday.c
+++ b/lib/strtoday.c
@@ -14,6 +14,7 @@
 #include "atoi/str2i/str2s.h"
 #include "getdate.h"
 #include "prototypes.h"
+#include "string/ctype/strisascii/strisdigit.h"
 #include "string/strchr/stpspn.h"
 #include "string/strcmp/streq.h"
 
@@ -35,7 +36,6 @@
 long strtoday (const char *str)
 {
 	time_t t;
-	bool isnum = true;
 	const char *s = str;
 
 	/*
@@ -54,14 +54,9 @@ long strtoday (const char *str)
 		s++;
 	}
 	s = stpspn(s, " ");
-	while (isnum && !streq(s, "")) {
-		if (!isdigit (*s)) {
-			isnum = false;
-		}
-		s++;
-	}
-	if (isnum) {
+	if (strisdigit(s)) {
 		long retdate;
+
 		if (str2sl(&retdate, str) == -1)
 			return -2;
 		return retdate;
diff --git a/lib/subordinateio.c b/lib/subordinateio.c
index bf02328e7..229f27cb3 100644
--- a/lib/subordinateio.c
+++ b/lib/subordinateio.c
@@ -22,6 +22,7 @@
 #include "alloc/realloc.h"
 #include "alloc/reallocf.h"
 #include "atoi/str2i/str2u.h"
+#include "string/ctype/strisascii/strisdigit.h"
 #include "string/sprintf/snprintf.h"
 #include "string/strcmp/streq.h"
 
@@ -926,22 +927,12 @@ int list_owner_ranges(const char *owner, enum subid_type id_type, struct subid_r
 	return count;
 }
 
-static bool all_digits(const char *str)
-{
-	int i;
-
-	for (i = 0; str[i] != '\0'; i++)
-		if (!isdigit(str[i]))
-			return false;
-	return true;
-}
-
 static int append_uids(uid_t **uids, const char *owner, int n)
 {
 	int    i;
 	uid_t  owner_uid;
 
-	if (all_digits(owner)) {
+	if (strisdigit(owner)) {
 		i = sscanf(owner, "%d", &owner_uid);
 		if (i != 1) {
 			// should not happen