d1: October 6, 2023
d2: December 30, 1999
d3: January 1, 2000

d1 < d2? FALSE
d2 < d3? TRUE

next day d2: December 31, 1999
d2 < d3? TRUE
d2 = d3? FALSE
d2 > d3? FALSE

next day d2: January 1, 2000
d2 = d3? TRUE

initialized d1 to February 28, 1529
next day d1: March 1, 1529

initialized d1 to February 28, 1460
next day d1: February 29, 1460

initialized d1 to February 28, 1700
next day d1: March 1, 1700

initialized d1 to February 28, 1600
next day d1: February 29, 1600