Comment by LegionMammal978

It's frustrating when people just pick an arbitrary interpretation of old dates instead of actually looking at the context. Even beyond Julian vs. Gregorian leap-year rules, we also see historical variation in the start of the numbered year (January 1 vs. different dates in March). I'm not aware of any software that can represent all such dates as they appear in the primary sources: they always have to be translated through someone's manual effort, which can easily introduce misinterpretations. At least the day of week, when available, can help double-check a calendar assignment.