This gets even more complicated when you introduce dealing with foreign countries that actually don't follow the western calendar system. Such as the standard P

This gets even more complicated when you introduce dealing with foreign countries that actually don't follow the western calendar system. Such as the standard Persian calendar months and years. Also, did you know that the arabic Islamic calendar dates and the persian calendar dates don't agree? Because the traditional calendar dating back to the maximum geograhpical extent of the Persian empire is solar based, while the standard Islamic calendar is entirely lunar based. And the persian calendar is solar based and the year resets on Nowruz (new years day) around the spring equinox, but the practiced holidays are based on the lunar islamic months? But also some holidays like Nowruz are observed based on the solar date. This means you've got Nowruz occuring on approximately the same time in the weather season every year, while relative to the western calendar, notable holidays like Eid al-fitr and Eid al-adha and the start of Ramadan etc move backwards in calendar date approxiamtely 10 or 11 days per year. Some years Ramadan might occur in the middle of winter and much later on it will be in the middle of summer. This series of tweets doesn't even begin to get into the possible opportunities for confusion when working between three different calendar systems... And western countries where the standard work week is M-F but others where Friday is the day of rest and people work on a 6-day work week on a persian or arabic islamic calendar, but some companies give their employees a two day weekend so they're off on Friday and Saturday, but the local timezone equivalent of Sunday is definitely a normal workday... I could go on.