Ggtcf

I have a server app in Firebase cloud function with webhooks that receive data from a third party API.
In those data, I have times expressed in HH:mm local time (Central Europe Time).
I need to store them in Firestore as a timestamp UTC.

I tried this:

 //Evaluate offset between CET and UTC
 const dAujourdhui = new Date(); //07/03/2019 10:39 (UTC)
 const nHeureUTC = dAujourdhui.getUTCHours(); //10
 const nHeureLocal = dAujourdhui.getHours(); //10
 const timeZoneOffset = nHeureUTC - nHeureLocal //0!

 // Build a timestamp based on today's date and received time
 const currentDateString = dateFormat(dAujourdhui, "yyyy-mm-dd");
 var estimatedDateTimeOfArrival = new Date(`$currentDateString $timeReceivedFrom3rdPartyAPI`);

 // Add offset to hours
 const utcHour = estimatedDateTimeOfArrival.getUTCHours()
 estimatedDateTimeOfArrival.setHours(utcHour + timeZoneOffset)

 // Save to firestore
 ...

As you can see, I'm not able to evaluate the offset between CET and UTC as the code is run in a server set in UTC.

Any idea on how to solve it ?

Here is a solution I found to solve the problem.
It is based on an external library: 'moment-timezone'

 // Example's initial setup
 const dateFormat = require('dateformat')
 const moment = require('moment-timezone');
 const timeReceivedFrom3rdPartyAPI = "14:30" // Format "HH:mm", Paris time

 // Construct Date object with today's date and timeReceivedFrom3rdPartyAPI
 const currentDate = new Date();
 const currentDateString = dateFormat(currentDate, "yyyy-mm-dd");
 const estimatedDateTimeOfArrival = moment.tz(`$currentDateString $timeReceivedFrom3rdPartyAPI`, "Europe/Paris").toDate()

 console.log(estimatedDateTimeOfArrival)
 // 08/03/2018 13:30 UTC
 // Now I have UTC Full Date corresponding to timeReceivedFrom3rdPartyAPI