Create Subscription Calendar on Node.js

Subscription Calendar is typically a URL pointing to an .ics file hosted online. Calendar applications fetch updates from this URL at regular intervals. So, if the content of the online .ics file changes (because new events are added or existing events are modified), subscribers will see these changes in their calendar applications after the next refresh.

Here is a sample .ics to display bid opening dates

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//SanJoseCA//Calendar 1.0//EN
CALSCALE:GREGORIAN

BEGIN:VEVENT
UID:project-10334@sanjoseca.gov
SUMMARY:SJC New Belly Freight Facility and Receiving Center
DESCRIPTION:Project Manager: De Guzman, Chris
DTSTART:20231109T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10232@sanjoseca.gov
SUMMARY:SJC Terminal A Baggage Claim Escalators Replacement
DESCRIPTION:Project Manager: Ancheta, Lorimer
DTSTART:20230622T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10223@sanjoseca.gov
SUMMARY:BUILDING: Emergency Interim Shelter Rue Ferrari Expansion
DESCRIPTION:Project Manager: Castellanos, Francisco
DTSTART:20231020T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10131@sanjoseca.gov
SUMMARY:SJC Admin Parking Lot Safety Upgrades
DESCRIPTION:Project Manager: Ancheta, Lorimer
DTSTART:20230810T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10128@sanjoseca.gov
SUMMARY:PARK: BUNDLE - 9500 Hamann Tot Lot & 10121 Starbird Park Renovations
DESCRIPTION:Project Manager: Castellanos, Sarah
DTSTART:20230713T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10073@sanjoseca.gov
SUMMARY:Sanitary Sewer Condition Assessment FY 2022-2023 Package II
DESCRIPTION:Project Manager: Nguyen, Donie
DTSTART:20231109T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10071@sanjoseca.gov
SUMMARY:Sanitary Sewer Condition Assessment FY 2022-2023 Package I
DESCRIPTION:Project Manager: Franso, Linda
DTSTART:20231012T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10068@sanjoseca.gov
SUMMARY:TRAIL: Coyote Creek (I-280 Undercrossing Lighting)
DESCRIPTION:Project Manager: Correa, Leila
DTSTART:20230928T110000
END:VEVENT

BEGIN:VEVENT
UID:project-10027@sanjoseca.gov
SUMMARY:En Movimiento Bicycle Boulevards- STPL-5005(167)
DESCRIPTION:Project Manager: Leon, Diego
DTSTART:20231109T110000
END:VEVENT

BEGIN:VEVENT
UID:project-9998@sanjoseca.gov
SUMMARY:Rule 20B Underground District - Delmas/West San Fernando
DESCRIPTION:Project Manager: Simonis, David
DTSTART:20230810T110000
END:VEVENT

END:VCALENDAR

Use Node.js to create a dynamic iCalendar:

function formatDate(dateString) {
    let [month, day, year] = dateString.split('/');
    return `${year}${month}${day}T110000`; // The time is hardcoded to 11:00:00
}

app.get('/calendar-feed', (req, res) => {
    // Sample data - replace with database data
    let projects = [
        {
            id: 10334,
            name: "SJC New Belly Freight Facility and Receiving Center",
            manager: "De Guzman, Chris",
            date: "11/09/2023"
        },
        // ... other projects
    ];

    let icsContent = `BEGIN:VCALENDAR
        VERSION:2.0
        PRODID:-//SanJoseCA//Calendar 1.0//EN
        CALSCALE:GREGORIAN
    `;

    projects.forEach(project => {
        // Outputs something like "20231109T110000"
        let startDate = formatDate(project.date);
        icsContent += `BEGIN:VEVENT
              UID:project-${project.id}@sanjoseca.gov
              SUMMARY:${project.name}
              DESCRIPTION:Project Manager: ${project.manager}
              DTSTART:${startDate}
              END:VEVENT
            `;
    });

    icsContent += "END:VCALENDAR";
    icsContent = icsContent.replace(/\n +/g, '\n'); // Remove spaces after \n

    res.setHeader('Content-Type', 'text/calendar');
    res.setHeader('Content-Disposition', 'inline; filename=calendar.ics');
    res.send(icsContent); // Send dynamic calendar back
});

Common iCalendar fields

Field	Type	Description

Field	Type	Description
BEGIN/END	Required	Denote the beginning and end of an entity (e.g., `VCALENDAR`, `VEVENT`).
VERSION	Required	Specifies the version of the iCalendar specification.
PRODID	Required	Identifier for the product that created the iCalendar object.
UID	Required	A unique identifier for the event.
DTSTAMP	Required	Represents the date and time the iCalendar object was created.
SUMMARY	Optional	A brief description or title of the event.
DESCRIPTION	Optional	Detailed description of the event.
DTSTART	Optional	The start date/time of the event.
DTEND	Optional	The end date/time of the event.
LOCATION	Optional	Intended venue for the event.
RRULE	Optional	Recurrence rules for recurring events.
ATTENDEE	Optional	Specifies an attendee, often with an email address.
ORGANIZER	Optional	Specifies the organizer of the event, often with an email address.
URL	Optional	A URL associated with the event.
STATUS	Optional	Overall status or confirmation for the calendar entity (e.g., `CONFIRMED`, `TENTATIVE`).
CATEGORIES	Optional	Categories or subtypes of the calendar entity.
PRIORITY	Optional	Relative priority of a calendar entity (0 to 9).
TRANSP	Optional	Defines if the event shows as "busy" or "free". Common values: `TRANSPARENT`, `OPAQUE`.
ALARMS	Optional	Defines a reminder or an alarm for the event.

This table provides a high-level overview of some common iCalendar fields. For more detailed information, you would want to consult the official iCalendar specification (RFC 5545).

To gain a deeper understanding of these fields, consider exporting an .ics file from Outlook. By examining its contents, you can familiarize yourself with the various iCalendar fields in a practical context.