Change day/month language in DialogFlow bot - dialogflow-es

Question

I'm creating an assistant for an italian restaurant using DialogFlow.
I've set the language to spanish, and everything seems to go fine, but when i show the final date of the reservation it is shown in english (Friday and May in attached picture's case).
Is it possible to change it?
This is the code that generates the above particular response to a table booking process:
function createBooking(agent) {
let guests = agent.parameters.comensales;
let time = new Date(agent.parameters.time);
let date = new Date(agent.parameters.date);
let bookingDate = new Date(date);
var numeroReserva = Math.random().toString(16).slice(2, 8).toUpperCase();
bookingDate.setHours(time.getHours());
bookingDate.setMinutes(time.getMinutes());
let now = new Date();
if (guests < 1){
agent.add('You need to reserve a table for at least one person. Please try again!');
} else if (bookingDate < now){
agent.add(`No puedes reservar una fecha pasada. Por favor, inténtalo de nuevo!`);
} else if (bookingDate.getFullYear() > now.getFullYear()) {
agent.add(`No puedes hacer una reserva para ${bookingDate.getFullYear()} todavía. Por favor, elige una fecha en ${now.getFullYear()}.`);
} else {
let timezone = parseInt(agent.parameters.time.toString().slice(19,22));
bookingDate.setHours(bookingDate.getHours() + timezone);
agent.add(`Perfecto. He reservado una mesa para ${guests} el ${bookingDate.toString().slice(0,21)}`);
agent.add(`Tu código de reserva es: ${numeroReserva}`);
agent.add('Nos vemos pronto!');
agent.add('Buon appetito!');
}
}

Answer 1

The code running the fulfillment runs within Google's compute infrastructure which has a default locale/language of US English. When a request arrives for fullfilment from Dialog flow, that request carries with it the language that we are to use to respond. See the languageCode in the Webhook Request JSON. When we use the APIs in Node.js, it looks like this data is available in the agent.locale property.
Looking at the JavaScript Date object, we seem to have a method on it called toLocaleString() which converts a date/time into a string but additionally supplies the language (locale) to be used to create the language specific content and format. If we put all this together, we might find that the following code line may work:
agent.add(`Perfecto. He reservado una mesa para ${guests} el ${bookingDate.toLocalString(agent.locale).slice(0,21)}`);
This may take a few tests to get right. I'd start by logging agent.locale as a test to ensure that it has the value we expect/hope.

Answer 2

It's late but for those who face with this problem. You know you can do it like this:
let options = { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric',
hour12: false, hour: 'numeric', minute: 'numeric' };
var curr_date = new Date();
agent.add(`Sono le ` + curr_date.toLocaleString('it-IT', options));

Answer 3

If someone likes to use moment.js
you can add library to your project from fulfillment inline editor.
Go to Fulfillment, click on "package.json"
add the following lines in dependencies
"moment": "^2.24.0",
"moment-timezone": "^0.5.31"
Then back to index.js and add the following line to import it
const moment = require('moment-timezone');
and then you can handle like this in your function
if(agent.locale === 'en'){
moment.locale('en-US');
agent.add(`Now is ` + moment().tz(your_time_zone).format('LLLL'));
}
else if(agent.locale === 'it-IT' || agent.locale === 'it'){
moment.locale('it');
agent.add(`Sono le ` + moment().tz(your_time_zone).format('LLLL'));
}
The sample of response is " Sono le martedì 20 ottobre 2020 15:30"
or "Now is Tuesday, October 20, 2020 3:31 PM"