diff --git a/Annex/VectorClock/Utility.hs b/Annex/VectorClock/Utility.hs
index 1396dd54cb..76b74d9cd5 100644
--- a/Annex/VectorClock/Utility.hs
+++ b/Annex/VectorClock/Utility.hs
@@ -20,4 +20,14 @@ startVectorClock = go =<< getEnv "GIT_ANNEX_VECTOR_CLOCK"
 	go (Just s) = case parsePOSIXTime s of
 		Just t -> return (pure (CandidateVectorClock t))
 		Nothing -> timebased
-	timebased = return (CandidateVectorClock <$> getPOSIXTime)
+	-- Avoid using fractional seconds in the CandidateVectorClock.
+	-- This reduces the size of the packed git-annex branch by up
+	-- to 8%. 
+	--
+	-- Due to the use of vector clocks, high resolution timestamps are
+	-- not necessary to make clear which information is most recent when
+	-- eg, a value is changed repeatedly in the same second. In such a
+	-- case, the vector clock will be advanced to the next second after
+	-- the last modification.
+	timebased = return $
+		CandidateVectorClock . truncateResolution 0 <$> getPOSIXTime
diff --git a/CHANGELOG b/CHANGELOG
index 862e594492..0a350cd892 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -17,6 +17,8 @@ git-annex (10.20231130) UNRELEASED; urgency=medium
   * sync: Fix locking problems during merge when annex.pidlock is set.
   * Avoid a problem with temp file names ending in "." on certian
     filesystems that have problems with such filenames.
+  * Lower precision of timestamps in git-annex branch, which can reduce the
+    size of the branch by up to 8%.
 
  -- Joey Hess <id@joeyh.name>  Thu, 30 Nov 2023 14:48:12 -0400
 
diff --git a/Utility/TimeStamp.hs b/Utility/TimeStamp.hs
index b740d7bead..878d6f7299 100644
--- a/Utility/TimeStamp.hs
+++ b/Utility/TimeStamp.hs
@@ -1,6 +1,6 @@
 {- timestamp parsing and formatting
  -
- - Copyright 2015-2019 Joey Hess <id@joeyh.name>
+ - Copyright 2015-2023 Joey Hess <id@joeyh.name>
  -
  - License: BSD-2-clause
  -}
@@ -9,6 +9,7 @@ module Utility.TimeStamp (
 	parserPOSIXTime,
 	parsePOSIXTime,
 	formatPOSIXTime,
+	truncateResolution,
 ) where
 
 import Utility.Data
@@ -56,3 +57,10 @@ mkPOSIXTime n (d, dlen)
 
 formatPOSIXTime :: String -> POSIXTime -> String
 formatPOSIXTime fmt t = formatTime defaultTimeLocale fmt (posixSecondsToUTCTime t)
+
+{- Truncate the resolution to the specified number of decimal places. -}
+truncateResolution :: Int -> POSIXTime -> POSIXTime
+truncateResolution n t = secondsToNominalDiffTime $
+	fromIntegral ((truncate (nominalDiffTimeToSeconds t * d)) :: Integer) / d
+  where
+	d = 10 ^ n