diff --git a/libc/tzcode/bionic.cpp b/libc/tzcode/bionic.cpp
index 6d84303..182fa89 100644
--- a/libc/tzcode/bionic.cpp
+++ b/libc/tzcode/bionic.cpp
@@ -105,12 +105,18 @@
   int32_t unused; // Was raw GMT offset; always 0 since tzdata2014f (L).
 };
 
+// Returns -2 for a soft failure (where the caller should try another file),
+// -1 for a hard failure (where the caller should give up), and >= 0 is a
+// file descriptor whose offset points to the data for the given olson id in
+// the given file (and *entry_length is the size of the data).
 static int __bionic_open_tzdata_path(const char* path,
                                      const char* olson_id,
                                      int32_t* entry_length) {
   int fd = TEMP_FAILURE_RETRY(open(path, O_RDONLY | O_CLOEXEC));
   if (fd == -1) {
-    return -2; // Distinguish failure to find any data from failure to find a specific id.
+    // We don't log here, because this is quite common --- current devices
+    // aren't expected to have the old APK tzdata, for example.
+    return -2;
   }
 
   bionic_tzdata_header_t header = {};
@@ -119,49 +125,49 @@
     fprintf(stderr, "%s: could not read header of \"%s\": %s\n",
             __FUNCTION__, path, (bytes_read == -1) ? strerror(errno) : "short read");
     close(fd);
-    return -1;
+    return -2;
   }
 
   if (strncmp(header.tzdata_version, "tzdata", 6) != 0 || header.tzdata_version[11] != 0) {
     fprintf(stderr, "%s: bad magic in \"%s\": \"%.6s\"\n", __FUNCTION__, path, header.tzdata_version);
     close(fd);
-    return -1;
+    return -2;
   }
 
   if (TEMP_FAILURE_RETRY(lseek(fd, ntohl(header.index_offset), SEEK_SET)) == -1) {
     fprintf(stderr, "%s: couldn't seek to index in \"%s\": %s\n", __FUNCTION__, path, strerror(errno));
     close(fd);
-    return -1;
+    return -2;
   }
 
   if (ntohl(header.index_offset) > ntohl(header.data_offset)) {
     fprintf(stderr, "%s: invalid data and index offsets in \"%s\": %u %u\n",
             __FUNCTION__, path, ntohl(header.data_offset), ntohl(header.index_offset));
     close(fd);
-    return -1;
+    return -2;
   }
   const size_t index_size = ntohl(header.data_offset) - ntohl(header.index_offset);
   if ((index_size % sizeof(index_entry_t)) != 0) {
     fprintf(stderr, "%s: invalid index size in \"%s\": %zd\n", __FUNCTION__, path, index_size);
     close(fd);
-    return -1;
+    return -2;
   }
 
-  off_t specific_zone_offset = -1;
   char* index = reinterpret_cast<char*>(malloc(index_size));
   if (index == nullptr) {
     fprintf(stderr, "%s: couldn't allocate %zd-byte index for \"%s\"\n", __FUNCTION__, index_size, path);
     close(fd);
-    return -1;
+    return -2;
   }
   if (TEMP_FAILURE_RETRY(read(fd, index, index_size)) != static_cast<ssize_t>(index_size)) {
     fprintf(stderr, "%s: could not read index of \"%s\": %s\n",
             __FUNCTION__, path, (bytes_read == -1) ? strerror(errno) : "short read");
     free(index);
     close(fd);
-    return -1;
+    return -2;
   }
 
+  off_t specific_zone_offset = -1;
   size_t id_count = index_size / sizeof(index_entry_t);
   index_entry_t* entry = reinterpret_cast<index_entry_t*>(index);
   for (size_t i = 0; i < id_count; ++i) {
@@ -180,6 +186,9 @@
   free(index);
 
   if (specific_zone_offset == -1) {
+    // We found a valid tzdata file, but didn't find the requested id in it.
+    // Give up now, and don't try fallback tzdata files. We don't log here
+    // because for all we know the given olson id was nonsense.
     close(fd);
     return -1;
   }
@@ -188,11 +197,9 @@
     fprintf(stderr, "%s: could not seek to %ld in \"%s\": %s\n",
             __FUNCTION__, specific_zone_offset, path, strerror(errno));
     close(fd);
-    return -1;
+    return -2;
   }
 
-  // TODO: check that there's TZ_MAGIC at this offset, so we can fall back to the other file if not.
-
   return fd;
 }
 
@@ -204,8 +211,9 @@
   //    tried first because it allows us to test that the time zone updates
   //    via APK mechanism still works even on devices with the time zone
   //    module.
+  //    TODO: remove this when those devices are no longer supported.
   // 2: The time zone data module which contains the main copy. This is the
-  //    common case.
+  //    common case for current devices.
   // 3: The ultimate fallback: the non-updatable copy in /system.
 
 #if defined(__ANDROID__)
@@ -214,15 +222,15 @@
 
   fd = __bionic_open_tzdata_path("/data/misc/zoneinfo/current/tzdata",
                                  olson_id, entry_length);
-  if (fd >= 0) return fd;
+  if (fd >= -1) return fd;
 
   fd = __bionic_open_tzdata_path("/apex/com.android.tzdata/etc/tz/tzdata",
                                  olson_id, entry_length);
-  if (fd >= 0) return fd;
+  if (fd >= -1) return fd;
 
   fd = __bionic_open_tzdata_path("/system/usr/share/zoneinfo/tzdata",
                                  olson_id, entry_length);
-  if (fd >= 0) return fd;
+  if (fd >= -1) return fd;
 #else
   // On the host, we don't expect the hard-coded locations above to exist, and
   // we're not worried about security so we trust $ANDROID_DATA,
@@ -232,17 +240,17 @@
   char* path = make_path("ANDROID_DATA", "/misc/zoneinfo/current/tzdata");
   fd = __bionic_open_tzdata_path(path, olson_id, entry_length);
   free(path);
-  if (fd >= 0) return fd;
+  if (fd >= -1) return fd;
 
   path = make_path("ANDROID_TZDATA_ROOT", "/etc/tz/tzdata");
   fd = __bionic_open_tzdata_path(path, olson_id, entry_length);
   free(path);
-  if (fd >= 0) return fd;
+  if (fd >= -1) return fd;
 
   path = make_path("ANDROID_ROOT", "/usr/share/zoneinfo/tzdata");
   fd = __bionic_open_tzdata_path(path, olson_id, entry_length);
   free(path);
-  if (fd >= 0) return fd;
+  if (fd >= -1) return fd;
 #endif
 
   // Not finding any tzdata is more serious that not finding a specific zone,
@@ -253,5 +261,6 @@
     fprintf(stderr, "%s: couldn't find any tzdata when looking for %s!\n", __FUNCTION__, olson_id);
   }
 
+  // Otherwise we were successful.
   return fd;
 }