diff --git a/voeventdb/server/bin/voeventdb_dump_tarball.py b/voeventdb/server/bin/voeventdb_dump_tarball.py
index 2ded0ab..aaba713 100755
--- a/voeventdb/server/bin/voeventdb_dump_tarball.py
+++ b/voeventdb/server/bin/voeventdb_dump_tarball.py
@@ -1,16 +1,20 @@
 #!/usr/bin/env python
 
-import sys
-import os
 import argparse
+import datetime
+import gc
 import logging
-import glob
+import os
+import sys
+import textwrap
 
+import iso8601
+import pytz
+import voeventdb.server.database.config as dbconfig
+from argparse import RawTextHelpFormatter
 from sqlalchemy import create_engine
 from sqlalchemy.orm import Session
-
 from voeventdb.server.database import db_utils
-import voeventdb.server.database.config as dbconfig
 from voeventdb.server.database.models import Voevent
 from voeventdb.server.utils.filestore import write_tarball
 
@@ -20,6 +24,11 @@
 logger = logging.getLogger("voeventdb-dump")
 
 
+class MyFormatter(argparse.ArgumentDefaultsHelpFormatter,
+                  argparse.RawDescriptionHelpFormatter):
+    pass
+
+
 def handle_args():
     """
     Default values are defined here.
@@ -28,9 +37,28 @@ def handle_args():
     default_database_name = dbconfig.testdb_corpus_url.database
     parser = argparse.ArgumentParser(
         prog=os.path.basename(__file__),
-        formatter_class=argparse.ArgumentDefaultsHelpFormatter, )
+        # formatter_class=argparse.ArgumentDefaultsHelpFormatter,
+        formatter_class=MyFormatter,
+        description=textwrap.dedent("""\
+        Dump the raw VOEvents as XML files, collected into bzip2'd tarballs.
+
+        If start or end times are specified, then the range is start-inclusive
+        end-exclusive, i.e.
+
+            start <= author_datetime < end
+
+        NB when writing compressed tarballs in Python, the entire file is
+        composed in memory before writing to file. This means that setting
+        `nsplit` too large will result in very high memory usage! The default
+        value of 5000 seems to peak at <250MB of RAM (though this varies
+        according to the size of the VOEvent packets, and assumes
+        `prefetch=False`). Some quick tests suggest typical RAM usage
+            ~= 40MB + 30MB*(nsplit/1000) .
+        """),
+
+    )
     parser.add_argument('tarfile_pathstem',
-                        help='Path to tarball to create. '
+                        help='Path to tarball to create, e.g. `foobar`. '
                              'Suffix ``.tar.bz2`` will be appended.'
                         )
 
@@ -38,10 +66,34 @@ def handle_args():
                         default=str(default_database_name),
                         help='Database name')
 
-    parser.add_argument('-s', '--split',
+    parser.add_argument('-n', '--nsplit',
                         type=int,
-                        help="Output multiple files, `SPLIT` packets per tarball."
-                             "Naming convention is `<stem>.01.tar.bz2, <stem>.02.tar.bz2, ...`")
+                        default=5000,
+                        help=
+                        "Output multiple files, `NSPLIT` packets per tarball."
+                        "Naming convention is `<stem>.001.tar.bz2, <stem>.002.tar.bz2, ...`"
+                        )
+    parser.add_argument('-s', '--start',
+                        type=iso8601.parse_date,
+                        default=None,
+                        help="Filter events by author_date>=`START`")
+    parser.add_argument('-e', '--end',
+                        type=iso8601.parse_date,
+                        default=datetime.datetime.now(tz=pytz.UTC),
+                        help=
+                        "Filter events by author_date<`END`")
+    parser.add_argument('-p', '--prefetch', action='store_true', default=False,
+                        help=
+                        "Bulk-fetch XML packets from DB (~3x faster, but "
+                        "uses considerably more RAM, depending on value of "
+                        "`nsplit`.)"
+                        )
+    parser.add_argument('-a', '--all', action='store_true', default=False,
+                        help=
+                        "Ignore any datetime filters, dump **all** VOEvents."
+                        "(This option is provided to allow dumping of VOEvents"
+                        "with author_datetime=Null, which are otherwise ignored.)"
+                        )
     return parser.parse_args()
 
 
@@ -55,23 +107,47 @@ def main():
     n_packets_written = 0
 
     def get_tarfile_path():
-        if args.split:
-            suffix = '.{0:02d}.tar.bz2'.format(filecount)
+        if args.nsplit:
+            suffix = '.{0:03d}.tar.bz2'.format(filecount)
         else:
             suffix = '.tar.bz2'
         return args.tarfile_pathstem + suffix
 
     session = Session(bind=create_engine(dburl))
-    qry = session.query(Voevent).order_by(Voevent.id)
+    if args.prefetch:
+        qry = session.query(Voevent.ivorn, Voevent.xml)
+    else:
+        qry = session.query(Voevent)
+
+    if args.all:
+        logger.info("Dumping **all** packets currently in database")
+    else:
+        qry = qry.filter(Voevent.author_datetime < args.end)
+        if args.start is not None:
+            qry = qry.filter(Voevent.author_datetime >= args.start)
+            logger.info("Fetching packets from {}".format(args.start))
+        else:
+            logger.info("Fetching packets from beginning of time")
+        logger.info("...until: {}".format(args.end))
+    qry = qry.order_by(Voevent.id)
+
     n_matching = qry.count()
     logger.info("Dumping {} packets".format(n_matching))
-
+    start_time = datetime.datetime.now()
     while n_packets_written < n_matching:
-        voevents = qry.limit(args.split).offset(n_packets_written).all()
+        logger.debug("Fetching batch of up to {} packets".format(args.nsplit))
+        voevents = qry.limit(args.nsplit).offset(n_packets_written).all()
         ivorn_xml_tuples_gen = ((v.ivorn, v.xml) for v in voevents)
-        n_packets_written +=  write_tarball(ivorn_xml_tuples_gen, get_tarfile_path())
+        n_packets_written += write_tarball(ivorn_xml_tuples_gen,
+                                           get_tarfile_path())
+        elapsed = (datetime.datetime.now() - start_time).total_seconds()
+        logger.info(
+            "{} packets dumped so far, in {} ({:.0f} kilopacket/s)".format(
+                n_packets_written,
+                elapsed,
+                n_packets_written / elapsed
+            ))
         filecount += 1
-
     session.close()
     logger.info("Wrote {} packets".format(n_packets_written))
     return 0