How to make Google Cloud Function in the PDT or PST time zones

Question

I have a Google Cloud function that parses the day of the month from a UTC date For example myDate = Wed Nov 13 2019 02:05:00 GMT+0000 (UTC) This date is actually Tues Nov 12 in San Francisco time (PDT or PST).

But when in my Google cloud function, when I try to get the day of the month from this date with myDate.getDate(), I get 13 instead of 12.

I believe the reason why it returns 13 is because the time zone of the machine that the cloud function is running on is based on UTC time. When I run this function on my local machine, I get 12 as the correct date because my local machine is on PST time.

How do I make Google Cloud Function operated in the PDT or PST time zones so that the getDate() function gives me the correct date in the PDT or PST time zone?

Answer 1

2020 Update

As of Node 14, which is now in beta for Firebase as of Dec 11, 2020, you should be able to just do

process.env.TZ = 'America/Los_Angeles'

Answer 2

As Doug said, it's not possible to configure the timezone on a Cloud Functions server instance.

However, you don't need a library. Google Cloud Functions using NodeJS 8 or 10 can get the date in a particular time zone using the JavaScript Internationalization API:

let myDate = new Date("2019-11-13T02:05:00Z");  // the value you gave in the question
let s = myDate.toLocaleDateString('en-US', { timeZone: 'America/Los_Angeles' })
//=> "11/12/2019"

If you just want the numeric day of the month, you can extract it from the string from there.

+(s.split('/')[1])   //=> 12