Permanent Calendar

A fixed-date calendar and no time zones, researchers say | Human World | EarthSky

The same day always falls on the same date, year after year.
It maintains a 7-day week to preserve a day of religious observance (a Sabbath).

All months would have 30 days, except March, June, September, and December that are 31 days in duration.

Every 5 to 6 years, an extra week is added to the end of December to bring the calendar in sync with seasonal changes on Earth.

They also advocate abolishment of time zones in favor of Universal Time (UT), so that everyone across the world is on the same clock.