Date comparison works locally, but not on heroku - datetime

Question

In a Vuejs app, I currently have a button that is usable once a day. After it is clicked once, it is disabled until the following day. This works fine locally, but on heroku, the comparison does not seem to work.
Here is y date computed value in the vue component which returns true if the Act was created after 00:00 on the current date:
computed: {
...
actedToday() {
if (!!this.$store.getters.lastAct) {
let now = new Date();
console.log('this is now in actedToday computed: ', now);
let lastActDate = new Date(this.$store.getters.lastAct.created_at);
console.log('this is last act date in computed actedToday', this.$store.getters.lastAct.created_at);
console.log('was last Act today? ', lastActDate.getTime() > now.setHours(0,0,0,0));
return lastActDate.getTime() > now.setHours(0,0,0,0)
}
}
},
Here is what the console.log returns locally:
this is now in actedToday computed: Fri Oct 04 2019 15:20:24 GMT-0400 (Eastern Daylight Time)
ActButton.vue?0bb7:31 this is last act date in computed actedToday 2019-10-04T19:20:23.901Z
ActButton.vue?0bb7:32 was last Act today? true
And here is the analogous logs from the heroku app:
this is now in actedToday computed: Fri Oct 04 2019 15:21:18 GMT-0400 (Eastern Daylight Time)
ActButton.vue:31 this is last act date in computed actedToday 2019-10-04T03:30:22.266Z
ActButton.vue:32 was last Act today? false
In the first example, the comparison works as expected. In the second, although both dates are on the same day, the comparison returns false.

Answer 1

Your problem occurs due to different timezones. Your lastActDate is in Zulu-time (UTC, note the Z at the end) but your actedToday is in EDT. Using setHours(0,0,0,0) will give you the start of the day, but in the same timezone. Thus you have the following values:
//locally
now = Fri Oct 04 2019 15:20:24 GMT-0400 (Eastern Daylight Time)
now.setHours(0,0,0,0) = Fri Oct 04 2019 00:00:00 GMT-0400 (Eastern Daylight Time)
lastActDate = 2019-10-04T19:20:23.901Z = Fri Oct 04 2019 15:20:23.901 GMT-0400 (Eastern Daylight Time)
//heroku
now = Fri Oct 04 2019 15:21:18 GMT-0400 (Eastern Daylight Time)
now.setHours(0,0,0,0) = Fri Oct 04 2019 00:00:00 GMT-0400 (Eastern Daylight Time)
lastActDate = 2019-10-04T03:30:22.266Z = Fri Oct 03 2019 23:30:22.266 GMT-0400 (Eastern Daylight Time)
Thus heroku is right and your last action has not been "today". You should consider to use the same timezone in all of your dates.