select dump(begindate) from tab;
Typ=12 Len=7: 120,120,8,10,12,23,58

The format of the date datatype is

byte 1 - century (excess 100)  120 - 100 = 20
byte 2 - year (excess 100)  120 - 100 = 20
byte 3 - month = 8
byte 4 - day = 10
byte 5 - hour (excess 1) 12 - 1 = 11
byte 6 - minute (excess 1) 23 - 1 = 22
byte 7 - seconds (excess 1) 58 - 1 = 57

2020-08-10 11:22:57

发现表里面的数据还存在时间类型长度为4的值，
Typ=12 Len=4: 120,119,12,31
而且每次查询出来的时间还会变化？这是为什么呢？
Typ=12 Len=4: 120,119,12,31 2020-01-01 21:49:48