The International Fixed Calendar - <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;International_Fixed_Calendar" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;International_Fixed_Calendar</a> .<p>&gt; The calendar year has 13 months with 28 days each, divided into exactly 4 weeks (13 × 28 = 364). An extra day added as a holiday at the end of the year (December 29), sometimes called &quot;Year Day&quot;, does not belong to any week and brings the total to 365 days. ...<p>&gt; International Fixed Calendar inserts the extra day in leap year as June 29 - between Saturday June 28 and Sunday Sol 1.<p>Kodak used it for years. I recall that it helped with business operations because it was easier to compare costs and production between the months.