Why does the year in the Roman calendar doesn't refer to the date of Roma's creation ?
It is not a Roman calendar but a Julian calendar with Roman style as it was used during the middle ages.
Why does the conversion of a date to the Muslim calendar isn't the same between different software ?
The Muslim calendar is a lunar calendar Composed of 12 months of 29 or 30 days each and where the 9th month is the Ramadhan month. So it is based on the moon's phases and starts the first evening after the new moon, when it reappears just after sunset. The dates and hours of the new moons are calculated each year by the Bureau of Longitudes in Paris, and these dates and times are used in RamCal and in some countries like Turkey. But in other countries like Saudi Arabia or France, the first crescent must be observed with naked eyes by a faithfull. So in case of bad weather, there may be a shift of several days !
Q : Why do the Saints' days sometimes seem wrong ?
You can display for the Saints in RamCal the traditional dates or the present dates.
Traditional dates are those which were used till the 19th century and are sometimes different from present dates.