Detecting Time Zone

📘
How to store timezones in a database is covered in the Amazon RDS, Amazon Aurora guides.

Printing local time in a visitor's timezone

Fastah API's locationData.tz response attribute provides the tzdata IANA-standard timezone identifier. This is supported widely in all programming languages to create a Date or Time object.

let response = {
    "locationData": {
        "tz": "America/New_York",
    }
};

let options = { timeZone: response.locationData.tz, timeZoneName: 'short' };
let localTime = new Intl.DateTimeFormat([], options).format(new Date());

console.log("The visitor is likely in timezone ", response.locationData.tz, ", where the local time is: ", localTime);

package main

import (
	"fmt"
	"time"
)

var response = map[string]map[string]string{
	"locationData": {
		"tz": "America/New_York",
	},
}

func main() {
	loc, _ := time.LoadLocation(response["locationData"]["tz"])
	localTime := time.Now().In(loc).Format("2006-01-02 15:04:05 MST")
	fmt.Println("The visitor is likely in timezone: ", response["locationData"]["tz"], ", where the local time is:", localTime)
}

from datetime import datetime
import pytz

response =  requests.get(url, headers=headers)
response = response.json()

tz = pytz.timezone(response['locationData']['tz'])
localTime = datetime.now(tz).strftime('%Y-%m-%d %H:%M:%S %Z')

print("The visitor is likely in timezone:", response['locationData']['tz'], ", where the local time is: ", localTime)

Schedule Events in Visitor's Time Zone

Generate future event timestamps in the visitor's local time zone for scheduling tasks like emails or cron jobs. This example schedules an event for 11 AM on the first day of next month, formatted as PostgreSQL timestamp with time zone.

let response = {
    "locationData": {
        "tz": "America/New_York",
    }
};

let now = new Date();
// Get the first day of next month at 11am
let firstDayNextMonth = new Date(now.getFullYear(), now.getMonth() + 1, 1, 11, 0, 0);
let options = { timeZone: response.locationData.tz, hour12: false, year: 'numeric', month: '2-digit', day: '2-digit', hour: '2-digit', minute: '2-digit', second: '2-digit' };
// Format the time to be Postgres friendly and concatenate the timezone
let formattedTime = new Intl.DateTimeFormat([], options).format(firstDayNextMonth) + " " + response.locationData.tz;

console.log(formattedTime);  // Output: 2023-11-01 11:00:00 America/New_York

package main

import (
	"fmt"
	"time"
)

var response = map[string]map[string]string{
	"locationData": {
		"tz": "America/New_York",
	},
}

func main() {
	loc, _ := time.LoadLocation(response["locationData"]["tz"])
	now := time.Now()
	// Get the first day of next month at 11am
	firstDayNextMonth := time.Date(now.Year(), now.Month()+1, 1, 11, 0, 0, 0, loc)
	// Format the time to be Postgres friendly and concatenate the timezone
	formattedTime := firstDayNextMonth.Format("2006-01-02 15:04:05 ") + response["locationData"]["tz"]
	fmt.Println(formattedTime)  // Output: 2023-11-01 11:00:00 America/New_York
}

from datetime import datetime, timedelta
import pytz

response =  requests.get(url, headers=headers)
response = response.json()

now = datetime.now()
# Get the first day of next month at 11am
first_day_next_month = datetime(now.year, now.month + 1, 1, 11, 0, 0)
tz = pytz.timezone(response['locationData']['tz'])
local_time = tz.localize(first_day_next_month)
# Format the time to be Postgres friendly and concatenate the timezone
formatted_time = local_time.strftime('%Y-%m-%d %H:%M:%S ') + response['locationData']['tz']

print(formatted_time)  # Output: 2023-11-01 11:00:00 America/New_York

Storing in a SQL database

The SQL-standard type timestamp with time zone (often aliased to timestamptz) allows storage of timezone context within a database timestamp type. The following example shows how to use IP to timezone information to set a database column value to (say) 10.30am at a future date in the user's timezone; particularly handy for maximizing open rates in a say a marketing email tool, or just for good ol' courtesy's sake!

CREATE TABLE next_email_time (event_time timestamp with time zone);
-- Using IP to user timezone mapping, configure a future email to be send in user's waking hours
INSERT INTO next_email_time (event_time) 
VALUES ('2024-01-15 10:30:00'::TIMESTAMPTZ AT TIME ZONE 'Asia/Kathmandu');