GatsbyJS - Last Updated

In gatsby-node.js, add modifiedTime, which can be derived from parent node (File), to MarkdownRemark node:

exports.onCreateNode = ({ node, getNode, actions }) => {
  const { createNodeField } = actions;
  if (node.internal.type === `MarkdownRemark`) {
    // ...
    const parent = getNode(node.parent);
    createNodeField({
      node,
      name: `modifiedTime`,
      value: parent.modifiedTime.slice(0, 10),
    });
  }
};

Then query it like this:

query($slug: String!) {
  markdownRemark(fields: { slug: { eq: $slug } }) {
    ...
    fields {
      modifiedTime
    }
  }
}