diff --git a/main-actions/src/main/scala/sbt/compiler/Eval.scala b/main-actions/src/main/scala/sbt/compiler/Eval.scala
index 3bd69b09a..829a8c777 100644
--- a/main-actions/src/main/scala/sbt/compiler/Eval.scala
+++ b/main-actions/src/main/scala/sbt/compiler/Eval.scala
@@ -21,6 +21,7 @@ import java.net.URLClassLoader
 import Eval.{ getModule, getValue, WrapValName }
 
 import sbt.io.{ DirectoryFilter, FileFilter, GlobFilter, Hash, IO, Path }
+import sbt.io.Milli.getModifiedTime
 
 // TODO: provide a way to cleanup backing directory
 
@@ -485,7 +486,8 @@ private[sbt] object Eval {
   def filesModifiedBytes(fs: Array[File]): Array[Byte] =
     if (fs eq null) filesModifiedBytes(Array[File]()) else seqBytes(fs)(fileModifiedBytes)
   def fileModifiedBytes(f: File): Array[Byte] =
-    (if (f.isDirectory) filesModifiedBytes(f listFiles classDirFilter) else bytes(f.lastModified)) ++
+    (if (f.isDirectory) filesModifiedBytes(f listFiles classDirFilter)
+     else bytes(getModifiedTime(f))) ++
       bytes(f.getAbsolutePath)
   def fileExistsBytes(f: File): Array[Byte] =
     bytes(f.exists) ++
diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 1f2dcfd3a..88fbdcca0 100755
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -47,6 +47,7 @@ import sbt.io.{
   DirectoryFilter,
   Hash
 }, Path._
+import sbt.io.Milli.getModifiedTime
 import sbt.librarymanagement.Artifact.{ DocClassifier, SourceClassifier }
 import sbt.librarymanagement.Configurations.{
   Compile,
@@ -2315,7 +2316,7 @@ object Classpaths {
         case Some(period) =>
           val fullUpdateOutput = cacheDirectory / "out"
           val now = System.currentTimeMillis
-          val diff = now - fullUpdateOutput.lastModified()
+          val diff = now - getModifiedTime(fullUpdateOutput)
           val elapsedDuration = new FiniteDuration(diff, TimeUnit.MILLISECONDS)
           fullUpdateOutput.exists() && elapsedDuration > period
       }
diff --git a/main/src/main/scala/sbt/internal/LibraryManagement.scala b/main/src/main/scala/sbt/internal/LibraryManagement.scala
index a245344dc..a594d0439 100644
--- a/main/src/main/scala/sbt/internal/LibraryManagement.scala
+++ b/main/src/main/scala/sbt/internal/LibraryManagement.scala
@@ -13,6 +13,7 @@ import sbt.internal.librarymanagement._
 import sbt.librarymanagement._
 import sbt.librarymanagement.syntax._
 import sbt.util.{ CacheStore, CacheStoreFactory, Logger, Tracked }
+import sbt.io.Milli.getModifiedTime
 
 private[sbt] object LibraryManagement {
 
@@ -126,7 +127,7 @@ private[sbt] object LibraryManagement {
   }
 
   private[this] def fileUptodate(file: File, stamps: Map[File, Long]): Boolean =
-    stamps.get(file).forall(_ == file.lastModified)
+    stamps.get(file).forall(_ == getModifiedTime(file))
 
   private[sbt] def transitiveScratch(
       lm: DependencyResolution,
diff --git a/project/SiteMap.scala b/project/SiteMap.scala
index ed1f5239e..2cfb5d8ea 100644
--- a/project/SiteMap.scala
+++ b/project/SiteMap.scala
@@ -68,6 +68,8 @@ object SiteMap {
   // generates a string suitable for a sitemap file representing the last modified time of the given File
   private[this] def lastModifiedString(f: File): String = {
     val formatter = new java.text.SimpleDateFormat("yyyy-MM-dd")
+    // TODO: replace lastModified() with sbt.io.Milli.getModifiedTime(), once the build
+    // has been upgraded to a version of sbt that includes sbt.io.Milli.
     formatter.format(new java.util.Date(f.lastModified))
   }
   // writes the provided XML node to `output` and then gzips it to `gzipped` if `gzip` is true
diff --git a/project/Util.scala b/project/Util.scala
index 89556cd2e..0b87b02db 100644
--- a/project/Util.scala
+++ b/project/Util.scala
@@ -105,6 +105,8 @@ object Util {
     val timestamp = formatter.format(new Date)
     val content = versionLine(version) + "\ntimestamp=" + timestamp
     val f = dir / "xsbt.version.properties"
+    // TODO: replace lastModified() with sbt.io.Milli.getModifiedTime(), once the build
+    // has been upgraded to a version of sbt that includes sbt.io.Milli.
     if (!f.exists || f.lastModified < lastCompilationTime(analysis) || !containsVersion(f, version)) {
       s.log.info("Writing version information to " + f + " :\n" + content)
       IO.write(f, content)