Add option to get date in local or specified time zone

[mono0x]

Summary

Add option to get date in local or specified time zone.

Basic example

Add option to date type.

  query blogListQuery($skip: Int!, $limit: Int!) {
    ...
    allMarkdownRemark(...) {
      edges {
        node {
          ...
          frontmatter {
            date(formatString: "MMMM DD, YYYY", local: true) <-- use local time zone
            date(formatString: "MMMM DD, YYYY", tz: "Asia/Tokyo") <-- use specified time zone
          }
        }
      }
    }
  }

and/or add option to gatsby-config.js.

Motivation

Display date in an easy-to-understand way for main readers of the website.

[wardpeet]

Why do you want to do this inside the query and not inside the page or component itself?

[mono0x]

Thank you for your comment. I didn't know I can get raw string of the date if formatString is not specified.

gatsby/packages/gatsby/src/schema/types/type-date.js

Line 120 in 445f5ff

return date

I could display date in local time zone using following query and page.

  query blogListQuery($skip: Int!, $limit: Int!) {
    ...
    allMarkdownRemark(...) {
      edges {
        node {
          ...
          frontmatter {
            date
          }
        }
      }
    }
  }

import moment from 'moment'

<small>{moment(node.frontmatter.date).local().format(`MMMM DD, YYYY`)}</small>

Therefore, I think that applying time zone in query is not absolutely necessary. However, if Gatsby supports formatString, it is more natural to be able to specify time zone of formatted time.

[KyleAMathews]

Re-opening this as it's a valid use case as if you're displaying dates e.g. for an event, you often know what time zone you want to display and it'd be nice to generate that at build-time vs having to load a library for it. Intl is close to being widely usable ~90% but not quite there https://caniuse.com/?search=intl