im just curious, roman calendar question?

The Romans had various calendars through their history, with the final form being the Julian calendar. That one had 365 days and a leap year with an extra day every four years. Like now, that made the average year 365.25 days long. In western Europe, it remained in use until late in the sixteenth century. It's replacement by the Gregorian calendar was more like a reform. The year, for example, got to begin in January rather than March or, in some cases, at Easter.

Earlier Roman calendars apparently started of by counting 304 days.

Update

"my question is y did they do that extra day and 2 days for leap years

they could've just made it 364 days long right?"

Inconveniently, a year now happens to be based on a natural event with its own duration; namely, the length of time it takes the Earth to orbit the Sun, and that's approximately 365.26 days. If that gets ignored, then it has complications for the calendar over the centuries. For example, if we had a 364 day calendar, then natural reality would mean that today's date, (December 30th) would begin next year late at night on what's now December 28th. (We'd probably opt for it replacing December 29th.) And if that approach continued, then December 30th would eventually be in the natural autumn and then, some time later, during the natural summer. At the same speed, the usual summer holiday dates of European schools would drift into the spring and then the winter.

That drifting effect, even with a leap year built in, is part of the reason that the Julian calendar got reformed, and New Year got shoved into January rather than March or, in some places, Easter. Similarly, the literal tenth month (December) became the twelth. The literal eighth month (October) became the tenth. ('Dec' means 'ten' and 'oct' is 'eight'.)

There are 365 days per year

(except leap years = 366, because there are really 365.25 days per year).

This is 52 weeks plus 1 day, which is why 30 Dec 2010 was a Thursday and 30 Dec 2011 is a Friday. 30 Dec 2012 is a Sunday because 366 days for the leap year = 52 weeks + 2 days