This is actually not that a big deal, in many countries, like Afghanistan and Iran, people observe 3 different calendars for different purposes and they all drift from each other! That is, 1st Jan (Georgian) is not always 24th Jaddi/Dey (Afghan/Iranian - Solar) nor 7th of 7th Jumada i-ula (Lunar/Islamic)..

So people use calendars that look like this for each day: https://en.wikipedia.org/wiki/Rumi_calendar#/media/File:1911...