Props to the Mayans, whose dates are (almost) a base-20 number counting from the Mayan date of creation. It's not fully base 20, because the 2nd digit only counts to 18 because 360 is close enough to a year. So 13.0.5.17.19 is followed by 13.0.6.0.0 instead of 13.0.5.18.0. Bonus points: no leap years to worry about!
The downside is that their full calendar is somewhat more complicated, so they would say that today is (checks) 13.0.8.11.11 8 Chuwin 9 Sek, and tomorrow is 13.0.8.11.12 9 Eb' 10 Sek (that Tzolkin calendar component doesn't work like our months do!).
The downside is that their full calendar is somewhat more complicated, so they would say that today is (checks) 13.0.8.11.11 8 Chuwin 9 Sek, and tomorrow is 13.0.8.11.12 9 Eb' 10 Sek (that Tzolkin calendar component doesn't work like our months do!).