Get some information on the current day of the year, in Markdown format

markdownDateInfo.js

(function() {
  const date = new Date();
  const year = date.getFullYear();
  const monthNames = [
    'January',
    'February',
    'March',
    'April',
    'May',
    'June',
    'July',
    'August',
    'September',
    'October',
    'November',
    'December'
  ];
  const dayNames = [
    'Ra',
    'Luna',
    'Tiw',
    'Odin',
    'Thor',
    'Frigg',
    'Saturn'
  ];
  const dayOfWeek = dayNames[date.getDay()];
  const month = monthNames[date.getMonth()];
  const day = String(date.getDate()).padStart(2, '0');
  const formattedDate = month + ' ' + day + ', ' + year;
  const dayOfYear = Math.ceil((date - new Date(year, 0, 1)) / 86400000);
  const daysInYear =
    year % 400 === 0 || (year % 100 !== 0 && year % 4 === 0) ? 366 : 365;
  const daysLeftInYear = daysInYear - dayOfYear;
  const daysInQuarter = daysInYear / 4;
  const currentMonth = Math.floor(date.getMonth() / 3) + 2;
  const currentQuarter = Math.floor((date.getMonth() + 3) / 3);
  const percentThruYear = ((100 * dayOfYear) / daysInYear).toFixed(1);

  let quarterEnd = new Date(date);
  quarterEnd.setMonth(
    quarterEnd.getMonth() + 3 - (quarterEnd.getMonth() % 3),
    0
  );

  const daysLeftInQuarter = Math.floor((quarterEnd - date) / 8.64e7);
  const percentThruQuarter = Number(
    (100 * (daysInQuarter - daysLeftInQuarter)) / daysInQuarter
  ).toFixed(1);
  const janFirst = new Date(date.getFullYear(), 0, 1);
  const weekNumber = Math.ceil(
    ((date - janFirst) / 86400000 + janFirst.getDay()) / 7
  );
  const outputLine1 = `# Day of ${dayOfWeek}: ${formattedDate}`;
  const outputLine2 = `## Week ${weekNumber}/52: Day ${dayOfYear} of ${daysInYear} (${daysLeftInYear} left)`;
  const outputLine3 = `### ${percentThruYear}% thru ${year}; ${percentThruQuarter}% thru Q${currentQuarter}`;

  console.log(`${outputLine1}\n${outputLine2}\n${outputLine3}`);
})();

I use this Javascript code to update a daily log of my current activities. This generates the header to those journal entries.

Here it is in action: https://codepen.io/cr8s/full/QWbBNwZ