Creating a Time Zone Converter with Streamlit

6 steps on how to build your own converter

Posted in Advocate Posts,
Creating a Time Zone Converter with Streamlit

Hey, community! 👋

My name is Vinícius, and I’m a Data Analyst and LaTeX Editor.

I love solving problems and assisting customers with technology. When I ask a customer about a delivery deadline, they usually tell me a day and time in a different time zone than mine (e.g., 4 PM PST). Since I’m from Brazil, I have to convert it from PST to UTC+x, where "+x" refers to an offset that can be positive or negative.

There are lots of tools for time zone conversion, but I wanted something simple, intuitive, and ad-free. So I made a Streamlit app that converts a time zone from PST to UTC for any country! 👏

In this post, I’ll show you how to build it in six steps:

  1. Import the required Python modules/package
  2. Create a set of continents and countries
  3. Configure the Streamlit page, header, and dropdown menu
  4. Get the corresponding UTC+x time zone
  5. Display the resulting time
  6. Apply a custom dark theme
You can go straight to the app and the GitHub repo, if you’d like to skip reading.

But first, let’s talk about…

How does the Time Zone Converter work?

The way it works is super simple:

  1. The user selects a continent and a country.
  2. The corresponding time zone (in "UTC+x" format) is obtained based on the user's selection.
  3. The user enters a PST time to be converted into the associated time obtained from step (2).
  4. The resulting time for the selected country is displayed in the app.


Now, let’s help you develop your own converter!

1. Import the required Python modules/package

# Required Python modules/packages
import streamlit as st         # Streamlit framework 
from datetime import datetime  # For date and time
import pytz                    # For time zones

2. Create a set of continents and countries in the time zone context

# Create a dictionary with country name and corresponding timezone
timezone_dict = {
    "North America": {
        "United States": "America/New_York",
        "Canada": "America/Toronto",
        "Mexico": "America/Mexico_City",
        "Jamaica": "America/Jamaica",
        "Costa Rica": "America/Costa_Rica",
        "Bahamas": "America/Nassau",
        "Honduras": "America/Tegucigalpa",
        "Cuba": "America/Havana",
        "Dominican Republic": "America/Santo_Domingo"
    "South America": {
        "Brazil": "America/Sao_Paulo",
        "Argentina": "America/Argentina/Buenos_Aires",
        "Chile": "America/Santiago",
        "Colombia": "America/Bogota",
        "Peru": "America/Lima",
        "Uruguay": "America/Montevideo",
        "Ecuador": "America/Guayaquil",
        "Bolivia": "America/La_Paz",
        "Paraguay": "America/Asuncion",
        "Venezuela": "America/Caracas"
    "Europe": {
        "United Kingdom": "Europe/London",
        "France": "Europe/Paris",
        "Germany": "Europe/Berlin",
        "Italy": "Europe/Rome",
        "Spain": "Europe/Madrid",
        "Russia": "Europe/Moscow",
        "Turkey": "Europe/Istanbul",
        "Greece": "Europe/Athens",
        "Poland": "Europe/Warsaw",
        "Ukraine": "Europe/Kiev"
    "Asia": {
        "India": "Asia/Kolkata",
        "Japan": "Asia/Tokyo",
        "China": "Asia/Shanghai",
        "Saudi Arabia": "Asia/Riyadh",
        "South Korea": "Asia/Seoul",
        "Indonesia": "Asia/Jakarta",
        "Malaysia": "Asia/Kuala_Lumpur",
        "Vietnam": "Asia/Ho_Chi_Minh",
        "Philippines": "Asia/Manila",
        "Thailand": "Asia/Bangkok"
    "Oceania": {
        "Australia": "Australia/Sydney",
        "New Zealand": "Pacific/Auckland",
        "Fiji": "Pacific/Fiji",
        "Papua New Guinea": "Pacific/Port_Moresby",
        "Samoa": "Pacific/Apia",
        "Tonga": "Pacific/Tongatapu",
        "Solomon Islands": "Pacific/Guadalcanal",
        "Vanuatu": "Pacific/Efate",
        "Kiribati": "Pacific/Tarawa",
        "New Caledonia": "Pacific/Noumea"

# Create a list of continents
continents = ["North America", "South America", "Europe", "Asia", "Oceania"]

3. Configure the Streamlit page, header, and dropdown menu for continent and country selection

# Streamlit app page setup
    page_title='Time Zone Coverter', 
        'About': """This app is intended to select a country, get its 
        time zone in UTC format  and have its correspondent result 
        from a user-entered PST time."""

# Main header
st.header('Time Zone Coverter Streamlit app')

# Add some blank space

# Create a dropdown to select a continent
continent = st.sidebar.selectbox("1. Select a continent", continents)

# Create a dropdown to select a country within the selected continent
countries = list(timezone_dict[continent].keys())
country = st.sidebar.selectbox("2. Select a country", countries)

4. Get the corresponding UTC+x time zone for the user selection

# Display the selected UTC offset
st.markdown("### :earth_americas: Corresponding UTC time:")
timezone = timezone_dict[continent][country]
utc_offset ='%z')
st.markdown(f"> **{country}** time zone is **UTC{utc_offset[:-2]}:{utc_offset[-2:]}**")

5. Display the resulting time—the informed PST time converted to UTC+x

# Add some blank space

# Create input for PST time
st.markdown("### :clock10: PST time to UTC converter:")
pst_input = st.text_input("Enter PST time (e.g., 10:00 AM PST)")

# Convert PST time to UTC+X (where X is the offset)
    pst_time = datetime.strptime(pst_input, "%I:%M %p PST")
    pst_time = pytz.timezone("US/Pacific").localize(pst_time, is_dst=None)
    target_time = pst_time.astimezone(pytz.timezone(timezone)).strftime("%I:%M %p %Z")
    st.markdown(f"> The corresponding time in **{country}** is **{target_time}**")
    :lock: Invalid input format. Please enter PST time in format 
    '<span style="color:#7ef471"><b> 10:00 AM PST </b></span>'
    """, unsafe_allow_html=True)

6. Apply a custom dark theme by creating a .streamlit folder with this config.toml file


If you want to improve your Time Zone Converter, here are some suggestions:

  • Replace the set of time zones for countries/continents with an API. Some alternatives are TimezoneDB and GeoNames, to name a few. This would provide more options for countries and even work with more cities. For example, Brazil has four different time zones.
  • Implement more time zone formats, such as GMT, EST, CET, and so on.

Feel free to use your creativity. 😄

Wrapping up

Thank you for reading my post! Now you know how to create a simple yet useful Time Zone Converter app. It can determine a time zone (in UTC+x format) for a user-selected country and provide a rough estimate for a "PST to UTC+X" time conversion. If you have any questions, please post them in the comments below or contact me via GitHub, LinkedIn, or Medium.

Happy Streamlit-ing! 🎈

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