It might actually have been easier. Our current time system is regular enough that you can get away with skipping many irregularities (leap year is pretty much the one that matters). If you were forced to regularly deal with time conversions, you would just accept that different people have different times and you just need to convert.

This is still the case, since timezone differences affect day boundaries.

This is sadly more of an urban legend. There recently was an article about this which also disproved this theory quite well, best seen in other civilizations that have no connection to the european one.

And iirc at least one country decided that was too simple, decided to gradually shift, then reverted, then did it in one go.