The first is a conversion problem because a Gregorian year is used instead of a revolutionary calender date.
The second is the biggest number of signed 64-bit integer (technically an unsigned integer could be used here because there are no negative values for denominations) but this would still not be sufficient to display a 1021. But it's the absolute biggest banknote denomination and I believe switching to a 128-bit solution (if that's even possible) just for a few entries isn't worth it.
9,223,372,036,854,775,808 (signed 264)
18,446,744,073,709,551,615 (unsigned 264)
1,000,000,000,000,000,000,000 (1021)
170,141,183,460,469,231,731,687,303,715,884,105,728 (signed 2128)
340,282,366,920,938,463,463,374,607,431,768,211,455 (unsigned 2128)