This is the most common way this happens in my experience - people naively assume that by giving just a date and not a time surely it wont do timezone conversio

This is the most common way this happens in my experience - people naively assume that by giving just a date and not a time surely it wont do timezone conversion, but it does (and even worse that behaviour is not at all consistent between different languages/systems). Oh and fun fact JS parses 'YYYY/MM/DD' (slashes instead of dashes) differently from the dashed format as well... The 'safe' way that I try to make everyone use for 'wall clock'/'business' dates is 'YYYY-MM-DDT00:00:00' (without the Z) - this unambiguously parses as 'this date in the current timezone' in basically every languages Date type and it's ISO 8601 compliant. However it's still a pain in the ass to keep straight when serializing as the 'default' output is usually a timezone converted UTC string (Z at the end).