Updating date helper to use UTC.

packages/string-templates/src/helpers/date.js

@@ -2,6 +2,7 @@ const dayjs = require("dayjs")
 dayjs.extend(require("dayjs/plugin/duration"))
 dayjs.extend(require("dayjs/plugin/advancedFormat"))
 dayjs.extend(require("dayjs/plugin/relativeTime"))
+dayjs.extend(require("dayjs/plugin/utc"))
 
 /**
  * This file was largely taken from the helper-date package - we did this for two reasons:
@@ -88,7 +89,11 @@ module.exports.date = (str, pattern, options) => {
 
   setLocale(config.str, config.pattern, config.options)
 
-  return dayjs(new Date(config.str)).format(config.pattern)
+  const date = dayjs(new Date(config.str)).utc()
+  if (config.pattern === "") {
+    return date.toISOString()
+  }
+  return date.format(config.pattern)
 }
 
 module.exports.duration = (str, pattern, format) => {

packages/string-templates/test/helpers.spec.js

@@ -356,6 +356,15 @@ describe("Cover a few complex use cases", () => {
     expect(validity).toBe(true)
   })
 
+  it("should test a case of attempting to get a UTC ISO back out after processing", async () => {
+    const date = new Date()
+    const input = `{{ date (subtract (date dateThing "x") 300000) "" }}`
+    const output = await processString(input, {
+      dateThing: date.toISOString(),
+    })
+    expect(output).toEqual(new Date(date.getTime() - 300000).toISOString())
+  })
+
   it("test a very complex duration output", async () => {
     const currentTime = new Date(1612432082000).toISOString(),
       eventTime = new Date(1612432071000).toISOString()