diff --git a/direct/src/directtools/DirectManipulation.py b/direct/src/directtools/DirectManipulation.py
index 631eb710cd..4007207516 100644
--- a/direct/src/directtools/DirectManipulation.py
+++ b/direct/src/directtools/DirectManipulation.py
@@ -1370,7 +1370,7 @@ class ObjectHandles(NodePath, DirectObject):
         self.setScalingFactor(1)
 
     def setScalingFactor(self, scaleFactor):
-        self.ohScalingFactor = self.ohScalingFactor * scaleFactor
+        self.ohScalingFactor = scaleFactor
         self.scalingNode.setScale(self.ohScalingFactor * self.directScalingFactor)
 
     def getScalingFactor(self):
diff --git a/direct/src/dist/FreezeTool.py b/direct/src/dist/FreezeTool.py
index bb06c69fe1..376940fbe0 100644
--- a/direct/src/dist/FreezeTool.py
+++ b/direct/src/dist/FreezeTool.py
@@ -81,6 +81,25 @@ defaultHiddenImports = {
     'pandas._libs.tslibs.conversion': ['pandas._libs.tslibs.base'],
 }
 
+
+# These are modules that import other modules but shouldn't pick them up as
+# dependencies (usually because they are optional).  This prevents picking up
+# unwanted dependencies.
+ignoreImports = {
+    'direct.showbase.PythonUtil': ['pstats', 'profile'],
+
+    'toml.encoder': ['numpy'],
+}
+
+if sys.version_info >= (3, 8):
+    # importlib.metadata is a "provisional" module introduced in Python 3.8 that
+    # conditionally pulls in dependency-rich packages like "email" and "pep517"
+    # (the latter of which is a thirdparty package!)  But it's only imported in
+    # one obscure corner, so we don't want to pull it in by default.
+    ignoreImports['importlib._bootstrap_external'] = ['importlib.metadata']
+    ignoreImports['importlib.metadata'] = ['pep517']
+
+
 # These are overrides for specific modules.
 overrideModules = {
     # Used by the warnings module, among others, to get line numbers.  Since
@@ -997,7 +1016,7 @@ class Freezer:
 
         # Scan the directory, looking for .py files.
         modules = []
-        for basename in os.listdir(pathname):
+        for basename in sorted(os.listdir(pathname)):
             if basename.endswith('.py') and basename != '__init__.py':
                 modules.append(basename[:-3])
 
@@ -1031,7 +1050,7 @@ class Freezer:
             modulePath = self.getModulePath(topName)
             if modulePath:
                 for dirname in modulePath:
-                    for basename in os.listdir(dirname):
+                    for basename in sorted(os.listdir(dirname)):
                         if os.path.exists(os.path.join(dirname, basename, '__init__.py')):
                             parentName = '%s.%s' % (topName, basename)
                             newParentName = '%s.%s' % (newTopName, basename)
@@ -2499,6 +2518,11 @@ class PandaModuleFinder(modulefinder.ModuleFinder):
         if name in self.badmodules:
             self._add_badmodule(name, caller)
             return
+
+        if level <= 0 and caller and caller.__name__ in ignoreImports:
+            if name in ignoreImports[caller.__name__]:
+                return
+
         try:
             self.import_hook(name, caller, level=level)
         except ImportError as msg:
@@ -2679,7 +2703,7 @@ class PandaModuleFinder(modulefinder.ModuleFinder):
             except OSError:
                 self.msg(2, "can't list directory", dir)
                 continue
-            for name in names:
+            for name in sorted(names):
                 mod = None
                 for suff in self.suffixes:
                     n = len(suff)
diff --git a/direct/src/dist/commands.py b/direct/src/dist/commands.py
index 9da0a06cfa..87b8ff7fe5 100644
--- a/direct/src/dist/commands.py
+++ b/direct/src/dist/commands.py
@@ -978,6 +978,7 @@ class build_apps(setuptools.Command):
 
         rootdir = os.getcwd()
         for dirname, subdirlist, filelist in os.walk(rootdir):
+            subdirlist.sort()
             dirpath = os.path.relpath(dirname, rootdir)
             if skip_directory(dirpath):
                 self.announce('skipping directory {}'.format(dirpath))
diff --git a/direct/src/dist/installers.py b/direct/src/dist/installers.py
index f1234d3ad1..d947d97237 100644
--- a/direct/src/dist/installers.py
+++ b/direct/src/dist/installers.py
@@ -4,6 +4,7 @@ import subprocess
 import sys
 import tarfile
 import zipfile
+import struct
 
 import panda3d.core as p3d
 
@@ -14,7 +15,8 @@ def create_zip(command, basename, build_dir):
         zf.write(build_dir, base_dir)
 
         for dirpath, dirnames, filenames in os.walk(build_dir):
-            for name in sorted(dirnames):
+            dirnames.sort()
+            for name in dirnames:
                 path = os.path.normpath(os.path.join(dirpath, name))
                 zf.write(path, path.replace(build_dir, base_dir, 1))
             for name in filenames:
@@ -28,16 +30,39 @@ def create_tarball(command, basename, build_dir, tar_compression):
     build_cmd = command.get_finalized_command('build_apps')
     binary_names = list(build_cmd.console_apps.keys()) + list(build_cmd.gui_apps.keys())
 
+    source_date = os.environ.get('SOURCE_DATE_EPOCH', '').strip()
+    if source_date:
+        max_mtime = int(source_date)
+    else:
+        max_mtime = None
+
     def tarfilter(tarinfo):
         if tarinfo.isdir() or os.path.basename(tarinfo.name) in binary_names:
             tarinfo.mode = 0o755
         else:
             tarinfo.mode = 0o644
+
+        # This isn't interesting information to retain for distribution.
+        tarinfo.uid = 0
+        tarinfo.gid = 0
+        tarinfo.uname = ""
+        tarinfo.gname = ""
+
+        if max_mtime is not None and tarinfo.mtime >= max_mtime:
+            tarinfo.mtime = max_mtime
+
         return tarinfo
 
-    with tarfile.open('{}.tar.{}'.format(basename, tar_compression), 'w|{}'.format(tar_compression)) as tf:
+    filename = '{}.tar.{}'.format(basename, tar_compression)
+    with tarfile.open(filename, 'w|{}'.format(tar_compression)) as tf:
         tf.add(build_dir, base_dir, filter=tarfilter)
 
+    if tar_compression == 'gz' and max_mtime is not None:
+        # Python provides no elegant way to overwrite the gzip timestamp.
+        with open(filename, 'r+b') as fp:
+            fp.seek(4)
+            fp.write(struct.pack("<L", max_mtime))
+
 
 def create_gztar(command, basename, build_dir):
     return create_tarball(command, basename, build_dir, 'gz')
@@ -128,6 +153,7 @@ def create_nsis(command, basename, build_dir):
     nsi_dir = p3d.Filename.fromOsSpecific(build_cmd.build_base)
     build_root_dir = p3d.Filename.fromOsSpecific(build_dir)
     for root, dirs, files in os.walk(build_dir):
+        dirs.sort()
         for name in files:
             basefile = p3d.Filename.fromOsSpecific(os.path.join(root, name))
             file = p3d.Filename(basefile)
diff --git a/direct/src/task/Task.py b/direct/src/task/Task.py
index 951bb13173..9002d5bd63 100644
--- a/direct/src/task/Task.py
+++ b/direct/src/task/Task.py
@@ -329,7 +329,7 @@ class TaskManager:
 
     def add(self, funcOrTask, name = None, sort = None, extraArgs = None,
             priority = None, uponDeath = None, appendTask = False,
-            taskChain = None, owner = None):
+            taskChain = None, owner = None, delay = None):
         """
         Add a new task to the taskMgr.  The task will begin executing
         immediately, or next frame if its sort value has already
@@ -382,12 +382,17 @@ class TaskManager:
                 is called when the task terminates.  This is all the
                 ownermeans.
 
+            delay: an optional amount of seconds to wait before starting
+                the task (equivalent to doMethodLater).
+
         Returns:
             The new Task object that has been added, or the original
             Task object that was passed in.
         """
 
         task = self.__setupTask(funcOrTask, name, priority, sort, extraArgs, taskChain, appendTask, owner, uponDeath)
+        if delay is not None:
+            task.setDelay(delay)
         self.mgr.add(task)
         return task
 
diff --git a/dtool/src/dtoolutil/pandaSystem.cxx b/dtool/src/dtoolutil/pandaSystem.cxx
index 590da9a33a..1d54cdd151 100644
--- a/dtool/src/dtoolutil/pandaSystem.cxx
+++ b/dtool/src/dtoolutil/pandaSystem.cxx
@@ -197,7 +197,11 @@ get_compiler() {
  */
 string PandaSystem::
 get_build_date() {
+#ifdef PANDA_BUILD_DATE_STR
+  return PANDA_BUILD_DATE_STR;
+#else
   return __DATE__ " " __TIME__;
+#endif
 }
 
 /**
diff --git a/dtool/src/interrogate/interrogate.cxx b/dtool/src/interrogate/interrogate.cxx
index 8a69843bb3..8a9d9fe113 100644
--- a/dtool/src/interrogate/interrogate.cxx
+++ b/dtool/src/interrogate/interrogate.cxx
@@ -544,7 +544,15 @@ main(int argc, char **argv) {
   // Make up a file identifier.  This is just some bogus number that should be
   // the same in both the compiled-in code and in the database, so we can
   // check synchronicity at load time.
-  int file_identifier = time(nullptr);
+  // We allow overriding this value by setting SOURCE_DATE_EPOCH to support
+  // reproducible builds.
+  int file_identifier;
+  const char *source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+  if (source_date_epoch != nullptr && source_date_epoch[0] != 0) {
+    file_identifier = atoi(source_date_epoch);
+  } else {
+    file_identifier = time(nullptr);
+  }
   InterrogateModuleDef *def = builder.make_module_def(file_identifier);
 
   pofstream * the_output_include = nullptr;
diff --git a/makepanda/makepanda.py b/makepanda/makepanda.py
index eac0015711..c7df213179 100755
--- a/makepanda/makepanda.py
+++ b/makepanda/makepanda.py
@@ -2598,6 +2598,14 @@ def CreatePandaVersionFiles():
     if GIT_COMMIT:
         pandaversion_h += "\n#define PANDA_GIT_COMMIT_STR \"%s\"\n" % (GIT_COMMIT)
 
+    # Allow creating a deterministic build by setting this.
+    source_date = os.environ.get("SOURCE_DATE_EPOCH")
+    if source_date:
+        # This matches the GCC / Clang format for __DATE__ __TIME__
+        source_date = time.gmtime(int(source_date))
+        source_date = time.strftime('%b %e %Y %H:%M:%S', source_date)
+        pandaversion_h += "\n#define PANDA_BUILD_DATE_STR \"%s\"\n" % (source_date)
+
     checkpandaversion_cxx = CHECKPANDAVERSION_CXX.replace("$VERSION1",str(version1))
     checkpandaversion_cxx = checkpandaversion_cxx.replace("$VERSION2",str(version2))
     checkpandaversion_cxx = checkpandaversion_cxx.replace("$VERSION3",str(version3))
diff --git a/panda/src/downloadertools/multify.cxx b/panda/src/downloadertools/multify.cxx
index bea4c5bedd..d649992b40 100644
--- a/panda/src/downloadertools/multify.cxx
+++ b/panda/src/downloadertools/multify.cxx
@@ -57,6 +57,7 @@ string dont_compress_str = "jpg,png,mp3,ogg";
 // Default text extensions.  May be overridden with -X.
 string text_ext_str = "txt";
 
+time_t source_date_epoch = (time_t)-1;
 bool got_record_timestamp_flag = false;
 bool record_timestamp_flag = true;
 
@@ -430,6 +431,12 @@ add_files(const vector_string &params) {
     needs_repack = true;
   }
 
+  if (multifile->get_record_timestamp() && source_date_epoch != (time_t)-1) {
+    if (multifile->get_timestamp() > source_date_epoch) {
+      multifile->set_timestamp(source_date_epoch);
+    }
+  }
+
   if (needs_repack) {
     if (!multifile->repack()) {
       cerr << "Failed to write " << multifile_name << ".\n";
@@ -533,6 +540,12 @@ kill_files(const vector_string &params) {
     }
   }
 
+  if (multifile->get_record_timestamp() && source_date_epoch != (time_t)-1) {
+    if (multifile->get_timestamp() > source_date_epoch) {
+      multifile->set_timestamp(source_date_epoch);
+    }
+  }
+
   bool okflag = true;
 
   if (multifile->needs_repack()) {
@@ -779,6 +792,11 @@ main(int argc, char **argv) {
     }
   }
 
+  const char *source_date_epoch_str = getenv("SOURCE_DATE_EPOCH");
+  if (source_date_epoch_str != nullptr && source_date_epoch_str[0] != 0) {
+    source_date_epoch = (time_t)strtoll(source_date_epoch_str, nullptr, 10);
+  }
+
   extern char *optarg;
   extern int optind;
   static const char *optflags = "crutxkvz123456789Z:T:X:S:f:OC:ep:P:F:h";
diff --git a/panda/src/express/multifile.I b/panda/src/express/multifile.I
index 128eb5297e..21462cc467 100644
--- a/panda/src/express/multifile.I
+++ b/panda/src/express/multifile.I
@@ -67,6 +67,17 @@ get_timestamp() const {
   return _timestamp;
 }
 
+/**
+ * Changes the overall mudification timestamp of the multifile.  Note that this
+ * will be reset to the current time every time you modify a subfile.
+ * Only set this if you know what you are doing!
+ */
+INLINE void Multifile::
+set_timestamp(time_t timestamp) {
+  _timestamp = timestamp;
+  _timestamp_dirty = true;
+}
+
 /**
  * Sets the flag indicating whether timestamps should be recorded within the
  * Multifile or not.  The default is true, indicating the Multifile will
diff --git a/panda/src/express/multifile.h b/panda/src/express/multifile.h
index 540bf434d2..99b5242127 100644
--- a/panda/src/express/multifile.h
+++ b/panda/src/express/multifile.h
@@ -59,6 +59,7 @@ PUBLISHED:
   INLINE bool needs_repack() const;
 
   INLINE time_t get_timestamp() const;
+  INLINE void set_timestamp(time_t timestamp);
 
   INLINE void set_record_timestamp(bool record_timestamp);
   INLINE bool get_record_timestamp() const;
diff --git a/panda/src/mathutil/boundingSphere.cxx b/panda/src/mathutil/boundingSphere.cxx
index 32e48adad9..beb6cb6309 100644
--- a/panda/src/mathutil/boundingSphere.cxx
+++ b/panda/src/mathutil/boundingSphere.cxx
@@ -112,6 +112,10 @@ xform(const LMatrix4 &mat) {
 
     // Transform the center
     _center = _center * mat;
+
+    if (cinf(_radius)) {
+      set_infinite();
+    }
   }
 }
 
diff --git a/pandatool/src/progbase/programBase.cxx b/pandatool/src/progbase/programBase.cxx
index fb6a4458ba..7486c4a942 100644
--- a/pandatool/src/progbase/programBase.cxx
+++ b/pandatool/src/progbase/programBase.cxx
@@ -201,14 +201,26 @@ write_man_page(std::ostream &out) {
   // Generate a date string for inclusion into the footer.
   char date_str[256];
   date_str[0] = 0;
-  time_t current_time = time(nullptr);
+  time_t current_time;
+  tm *today = nullptr;
 
-  if (current_time != (time_t) -1) {
-    tm *today = localtime(&current_time);
-    if (today == nullptr || 0 == strftime(date_str, 256, "%d %B %Y", today)) {
-      date_str[0] = 0;
+  // This variable overrides the time we write to the footer.
+  const char *source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+  if (source_date_epoch == nullptr || source_date_epoch[0] == 0 ||
+      (current_time = (time_t)strtoll(source_date_epoch, nullptr, 10)) <= 0) {
+    current_time = time(nullptr);
+    if (current_time != (time_t)-1) {
+      today = localtime(&current_time);
     }
   }
+  else {
+    // Format as UTC to avoid inconsistency being introduced due to timezones.
+    today = gmtime(&current_time);
+  }
+
+  if (today == nullptr || 0 == strftime(date_str, 256, "%d %B %Y", today)) {
+    date_str[0] = 0;
+  }
 
   out << " 1 \"" << date_str << "\" \""
       << PandaSystem::get_version_string() << "\" Panda3D\n";