Make start date and day of month aware of timezones (fixes #12555) (#12696)

* WIP: #12555

-dayOfMonth takes timezone into account on task update for monthly dailys
-startDate set to start of day in user's tz on task update for monthly
dailys
-tweaked a test so that it's actually testing something

* WIP: 12555

-task.startDate gets set to start of day in user's tz on task creation
and task update
-set preferences.timezoneOffset to nonzero value in certian test user objects
-removed date literals in test:api-v3:integration:tasks:PUT

test/api/v3/integration/tasks/POST-tasks_user.test.js

@@ -8,9 +8,14 @@ import {
 
 describe('POST /tasks/user', () => {
   let user;
+  let tzoffset;
+
+  before(async () => {
+    tzoffset = new Date().getTimezoneOffset();
+  });
 
   beforeEach(async () => {
-    user = await generateUser();
+    user = await generateUser({ 'preferences.timezoneOffset': tzoffset });
   });
 
   context('validates params', async () => {
@@ -544,7 +549,7 @@ describe('POST /tasks/user', () => {
       expect(task.everyX).to.eql(5);
       expect(task.daysOfMonth).to.eql([15]);
       expect(task.weeksOfMonth).to.eql([3]);
-      expect(new Date(task.startDate)).to.eql(now);
+      expect(new Date(task.startDate)).to.eql(new Date(now.setHours(0, 0, 0, 0)));
       expect(task.isDue).to.be.true;
       expect(task.nextDue.length).to.eql(6);
     });