Date and time data types include:
TIME_OF_DAY, time (the current time is a few minutes and a few seconds);
LTIME_OF_DAY, time (the current time is a few minutes and a few seconds, a few milliseconds);
DATE_AND_TIME, date + time, BCD code transferred, to milliseconds;
LDT, date + time, unsigned integer, to nanoseconds;
DTL, date + time, structure, to nanoseconds.
LDT and DTL actually express the same content, but the way they are expressed is different.
The range and precision of LDT and DTL are the same. DTL uses a structure to express it. There is also an expression of the day of the week, which is calculated according to the year, month and day.