diff --git a/src/Build/PackageReadme.props b/src/Build/PackageReadme.props
index 0f733c3..b53a49b 100644
--- a/src/Build/PackageReadme.props
+++ b/src/Build/PackageReadme.props
@@ -16,8 +16,8 @@
     <GeneratedPackageReadmeFileContents>
 ---;
 title: $(Title);
-lastmod: $([System.DateTimeOffset]::Now.ToString("yyyy-MM-ddTHH:mm:ss.ppppZ"));
-date: $([System.DateTimeOffset]::Now.ToString("yyyy-MM-ddTHH:mm:ss.ppppZ"));
+lastmod: $([System.DateTimeOffset]::Now.ToString("yyyy-mm-ddTHH:mm:ss.ffffzzzZ"));
+date: $([System.DateTimeOffset]::Now.ToString("yyyy-mm-ddTHH:mm:ss.ffffzzzZ"));
 license: $(PackageLicenseExpression);
 slug: $(MSBuildProjectName)-readme;
 version: $(PackageVersion);