Documentation/public-inbox-index.pod | 10 ++++++++++
 MANIFEST                             |  1 +
 lib/PublicInbox/Admin.pm             |  4 ++++
 lib/PublicInbox/SearchIdx.pm         | 33 +++++++++++++++++++++++----------
 lib/PublicInbox/V2Writable.pm        |  8 +++++++-
 script/public-inbox-index            |  3 +++
 t/reindex-time-range.t               | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++++

diff --git a/Documentation/public-inbox-index.pod b/Documentation/public-inbox-index.pod
index 57fedb69656d8857b85f2995738f8a9ba8ac160f..c92b6de43b3553a3efddddb4afb1f2a235303701 100644
--- a/Documentation/public-inbox-index.pod
+++ b/Documentation/public-inbox-index.pod
@@ -185,6 +185,16 @@
 Do not update the C<all> external index by default.  This negates
 all uses of C<-E> / C<--update-extindex=> on the command-line.
 
+=item --since=DATESTRING
+
+=item --after=DATESTRING
+
+=item --until=DATESTRING
+
+=item --before=DATESTRING
+
+Passed directly to L<git-log(1)> to limit changes for C<--reindex>
+
 =back
 
 =head1 FILES
diff --git a/MANIFEST b/MANIFEST
index 22b7df9bb89d497146c3e282ba013928ddef013d..122ceda0a7610ac893135cbaf4df8be60c994007 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -519,6 +519,7 @@ t/psgi_v2-old.eml
 t/psgi_v2.t
 t/purge.t
 t/qspawn.t
+t/reindex-time-range.t
 t/replace.t
 t/reply.t
 t/run.perl
diff --git a/lib/PublicInbox/Admin.pm b/lib/PublicInbox/Admin.pm
index dcf17cf51d7ae26236e4ca9ddfc80b277d701dc2..a17a632ceb8606d8ded62ae3398f62609103a12b 100644
--- a/lib/PublicInbox/Admin.pm
+++ b/lib/PublicInbox/Admin.pm
@@ -368,6 +368,10 @@ 		defined(my $v = $cfg->git_bool($s))
 					or die "`$git_key=$s' not boolean\n";
 		$opt->{$k} = $v;
 	}
+	for my $k (qw(since until)) {
+		my $v = $opt->{$k} // next;
+		$opt->{reindex} or die "--$k=$v requires --reindex\n";
+	}
 	$env;
 }
 
diff --git a/lib/PublicInbox/SearchIdx.pm b/lib/PublicInbox/SearchIdx.pm
index 5b0e44581d27f033588c514d1af59deb7941d9ab..e5c872d52fd3fd477f42301f7407acbd8d0061fb 100644
--- a/lib/PublicInbox/SearchIdx.pm
+++ b/lib/PublicInbox/SearchIdx.pm
@@ -750,7 +750,8 @@ sub index_sync {
 	my ($self, $opt) = @_;
 	delete $self->{lock_path} if $opt->{-skip_lock};
 	$self->with_umask(\&_index_sync, $self, $opt);
-	if ($opt->{reindex} && !$opt->{quit}) {
+	if ($opt->{reindex} && !$opt->{quit} &&
+			!grep(defined, @$opt{qw(since until)})) {
 		my %again = %$opt;
 		delete @again{qw(rethread reindex)};
 		index_sync($self, \%again);
@@ -775,8 +776,8 @@
 	# $newest may be undef
 	my $newest = $stk ? $stk->{latest_cmt} : ${$sync->{latest_cmt}};
 	if (defined($newest)) {
-		my $cur = $self->{mm}->last_commit || '';
-		if (need_update($self, $cur, $newest)) {
+		my $cur = $self->{mm}->last_commit;
+		if (need_update($self, $sync, $cur, $newest)) {
 			$self->{mm}->last_commit($newest);
 		}
 	}
@@ -786,7 +787,7 @@ 	$self->{mm}->{dbh}->commit;
 	my $xdb = $self->{xdb};
 	if ($newest && $xdb) {
 		my $cur = $xdb->get_metadata('last_commit');
-		if (need_update($self, $cur, $newest)) {
+		if (need_update($self, $sync, $cur, $newest)) {
 			$xdb->set_metadata('last_commit', $newest);
 		}
 	}
@@ -870,9 +871,14 @@ 	}
 
 	# Count the new files so they can be added newest to oldest
 	# and still have numbers increasing from oldest to newest
-	my $fh = $git->popen(qw(log --raw -r --pretty=tformat:%at-%ct-%H
-				--no-notes --no-color --no-renames --no-abbrev),
-				$range);
+	my @cmd = qw(log --raw -r --pretty=tformat:%at-%ct-%H
+			--no-notes --no-color --no-renames --no-abbrev);
+	for my $k (qw(since until)) {
+		my $v = $sync->{-opt}->{$k} // next;
+		next if !$sync->{-opt}->{reindex};
+		push @cmd, "--$k=$v";
+	}
+	my $fh = $git->popen(@cmd, $range);
 	my ($at, $ct, $stk, $cmt);
 	while (<$fh>) {
 		return if $sync->{quit};
@@ -928,10 +934,17 @@ 	waitpid($pid, 0) == $pid or die join(' ', @$cmd) .' did not finish';
 	$? == 0;
 }
 
-sub need_update ($$$) {
-	my ($self, $cur, $new) = @_;
+sub need_update ($$$$) {
+	my ($self, $sync, $cur, $new) = @_;
 	my $git = $self->{ibx}->git;
-	return 1 if $cur && !is_ancestor($git, $cur, $new);
+	$cur //= ''; # XS Search::Xapian ->get_metadata doesn't give undef
+
+	# don't rewind if --{since,until,before,after} are in use
+	return if $cur ne '' &&
+		grep(defined, @{$sync->{-opt}}{qw(since until)}) &&
+		is_ancestor($git, $new, $cur);
+
+	return 1 if $cur ne '' && !is_ancestor($git, $cur, $new);
 	my $range = $cur eq '' ? $new : "$cur..$new";
 	chomp(my $n = $git->qx(qw(rev-list --count), $range));
 	($n eq '' || $n > 0);
diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index 971b007b02d62e6c62ebe9ca6b536432e874e18e..36b84f5708ae27ff52e01d082b630bbdb1c439a9 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -876,6 +876,11 @@ 		my @cmd = (qw(rev-list --count), "$last..$latest_cmt");
 		chomp(my $n = $unit->{git}->qx(@cmd));
 		return if $n ne '' && $n == 0;
 	}
+	# don't rewind if --{since,until,before,after} are in use
+	return if (defined($last) &&
+			grep(defined, @{$sync->{-opt}}{qw(since until)}) &&
+			is_ancestor($self->git, $latest_cmt, $last));
+
 	last_epoch_commit($self, $unit->{epoch}, $latest_cmt);
 }
 
@@ -1337,7 +1342,8 @@ 		$self->lock_release;
 	}
 
 	# reindex does not pick up new changes, so we rerun w/o it:
-	if ($opt->{reindex} && !$sync->{quit}) {
+	if ($opt->{reindex} && !$sync->{quit} &&
+			!grep(defined, @$opt{qw(since until)})) {
 		my %again = %$opt;
 		$sync = undef;
 		delete @again{qw(rethread reindex -skip_lock)};
diff --git a/script/public-inbox-index b/script/public-inbox-index
index ca190a2e32d03fed0bb4200903a771cedb645bd7..053d8b9438cb52303549db864851a7c7828b7e27 100755
--- a/script/public-inbox-index
+++ b/script/public-inbox-index
@@ -25,6 +25,8 @@   --jobs=NUM          set or disable parallelization (NUM=0)
   --batch-size=BYTES  flush changes to OS after a given number of bytes
   --max-size=BYTES    do not index messages larger than the given size
   --reindex           index previously indexed data (if upgrading)
+  --since=DATE        limit --reindex to changes after DATE
+  --until=DATE        limit --reindex to changes before DATE
   --rethread          regenerate thread IDs (if upgrading, use sparingly)
   --prune             prune git storage on discontiguous history
   --verbose | -v      increase verbosity (may be repeated)
@@ -40,6 +42,7 @@ GetOptions($opt, qw(verbose|v+ reindex rethread compact|c+ jobs|j=i prune
 		fsync|sync! xapian_only|xapian-only
 		indexlevel|index-level|L=s max_size|max-size=s
 		batch_size|batch-size=s
+		since|after=s until|before=s
 		sequential-shard|seq-shard
 		no-update-extindex update-extindex|E=s@
 		fast-noop|F skip-docdata all C=s@ help|h))
diff --git a/t/reindex-time-range.t b/t/reindex-time-range.t
new file mode 100644
index 0000000000000000000000000000000000000000..59f5c2aa2db4b68c0f8e716a72d54c27f50dcb51
--- /dev/null
+++ b/t/reindex-time-range.t
@@ -0,0 +1,58 @@
+# Copyright (C) all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict; use v5.10.1; use PublicInbox::TestCommon;
+require_mods qw(DBD::SQLite);
+my $tmp = tmpdir();
+my $eml;
+my $cb = sub {
+	my ($im, $ibx) = @_;
+	$eml //= eml_load 't/utf8.eml';
+	for my $i (1..3) {
+		$eml->header_set('Message-ID', "<$i\@example.com>");
+		my $d = "Thu, 01 Jan 1970 0$i:30:00 +0000";
+		$eml->header_set('Date', $d);
+		$im->add($eml);
+	}
+};
+my %ibx = map {;
+	"v$_" => create_inbox("v$_", version => $_,
+			indexlevel => 'basic', tmpdir => "$tmp/v$_", $cb);
+} (1, 2);
+
+my $env = { TZ => 'UTC' };
+my ($out, $err);
+for my $v (sort keys %ibx) {
+	my $opt = { -C => $ibx{$v}->{inboxdir}, 1 => \$out, 2 => \$err };
+
+	($out, $err) = ('', '');
+	run_script([ qw(-index -vv) ], $env, $opt);
+	is($?, 0, 'no error on initial index');
+
+	for my $x (qw(until before)) {
+		($out, $err) = ('', '');
+		run_script([ qw(-index --reindex -vv),
+				"--$x=1970-01-01T02:00:00Z" ], $env, $opt);
+		is($?, 0, "no error with --$x");
+		like($err, qr! 1/1\b!, "$x only indexed one message");
+	}
+	for my $x (qw(after since)) {
+		($out, $err) = ('', '');
+		run_script([ qw(-index --reindex -vv),
+				"--$x=1970-01-01T02:00:00Z" ], $env, $opt);
+		is($?, 0, "no error with --$x");
+		like($err, qr! 2/2\b!, "$x only indexed one message");
+	}
+
+	($out, $err) = ('', '');
+	run_script([ qw(-index --reindex -vv) ], $env, $opt);
+	is($?, 0, 'no error on initial index');
+
+	for my $x (qw(since before after until)) {
+		($out, $err) = ('', '');
+		run_script([ qw(-index -v), "--$x=1970-01-01T02:00:00Z" ],
+			$env, $opt);
+		isnt($?, 0, "--$x fails on --reindex");
+	}
+}
+
+done_testing;