According to https://ftp.gnu.org/old-gnu/Manuals/glibc-2.2.3/html_chapter/libc_21.html
timelocal(2) is functionally identical to mktime(2), but more
mnemonically named. There is no timelocal(2) defined in musl libc.

--- a/snapper/AppUtil.cc
+++ b/snapper/AppUtil.cc
@@ -279,10 +279,10 @@
     {
 	struct tm s;
 	memset(&s, 0, sizeof(s));
-	const char* p = strptime(str.c_str(), "%F %T", &s);
+	const char* p = strptime(str.c_str(), "%Y-%m-%d %T", &s);
 	if (!p || *p != '\0')
 	    return (time_t)(-1);
-	return utc ? timegm(&s) : timelocal(&s);
+	return utc ? timegm(&s) : mktime(&s);
     }