Calculate the age of a person and write it to the event's description in your birthday calendar using Google Apps Script

README.md

Calculate the age of a person and write it to the event's description in your birthday calendar using Google Apps Script

This script uses Google Apps Script to access one's Google Calendar and calculate the age on a person's birthday. In the best case you have a custom calendar where your birthdays are stored at. If not, uncomment line 20 and use the filter function at the bottom.

Steps to setup everything

1. Head to https://script.google.com/home/my and create a new project. Rename the existing file Code.gs to your liking and paste the code from calculateAge.gs.
2. Paste your calendar ID in line 9 (you can find it in the Google Calendar Settings)
3. Make sure to add the birth year of a person to the location field (or customize the script)
4. Customize the message in line 36
5. Hit run and see the messages appear in your calendar events for the current year!
6. Create a trigger to run this every year to calculate the correct age

---

calculateAge.gs

const CALENDAR_ID = "[email protected]";
const TAG_NAME = 'calculatedAge';
const FORCE_OVERWRITE = false;

// Control for how many years in the future the age should be calculated
// Set to `1` to only cover the current year
const CALCULATE_FOR_YEARS = 2;

// Set to `true` to enable debug logging
const DEBUG = false;

/*
 * Calculate the age of birthday people in each year and add a short note in the description
 */
function calculateAge() {
  // Get Calendar 'Birthdays'
  const birthdayCal = CalendarApp.getCalendarById(CALENDAR_ID);

  const yearOfExecution = (new Date()).getFullYear()

  for (var i = 0; i < CALCULATE_FOR_YEARS; i++) {

    // Select date range of the year that is currently processed
    const currentYear = yearOfExecution + i;
    const start = new Date(currentYear + '-01-01');
    const end = new Date(currentYear + '-12-31');

    // Fetch events from Birthday Calendar
    var birthdays = birthdayCal.getEvents(start, end);

    // Filter Birthdays out of Default Calendar (if no specific Birthday Calendar is present)
    // birthdays = birthdays.filter(filterBirthdays);

    if (DEBUG) {
      Logger.log(`Scanning ${birthdays.length} birthdays in year ${currentYear} ...`)
    }

    for (var j = 0; j < birthdays.length; j++) {
      e = birthdays[j];

      // Year of birth is stored in the Location field of the event
      const birthYear = e.getLocation()
      const birthYearIsNotEmpty = birthYear !== ""

      if (birthYearIsNotEmpty) {
        const descriptionIsEmpty = e.getDescription() === ""
        const tagIsEmpty = isNaN(parseInt(e.getTag(TAG_NAME)))

        // Calculate the age if it has not been done before OR `FORCE_OVERWRITE` is true
        if ((descriptionIsEmpty && tagIsEmpty) || FORCE_OVERWRITE) {

          const calculatedAge = Math.round(currentYear - birthYear);

          // Customize the description here
          const description = e.getTitle() + ' wird heute ' + calculatedAge + ' Jahre!'
          e.setDescription(description);

          // Save calculated age in tag
          e.setTag(TAG_NAME, calculatedAge);

          if (DEBUG) {
            const logEntry = {
              name: e.getTitle(),
              birthyear: e.getLocation(),
              currentYear: Math.round(currentYear),
              calculatedAge: Math.round(calculatedAge),
            }

            Logger.log(`${description} \n ${JSON.stringify(logEntry, null, 2)}`)
          }
        }
      }
    }
  }
}

/*
 * Filter the birthdays out of the fetched events
 * Add additional filters if you don't have a specific Birthday Calendar
 */
function filterBirthdays(event) {
  // Add filter here (e.g. event.getColor === CalendarApp.Color.YELLOW)
  return event.isAllDayEvent();
}

@dribnus did you get it to work? Adding it to the title instead of the description should be as easy as

const previousTitle = e.getTitle()
e.setTitle(previousTitle + ' | Turns ' + calculatedAge + ' today!')

Didn't test it so, don't want to mess with my current script.