The TDateTime class inherits a val data member declared as a double that holds the date-time value. The integral part of a TDateTime value is the number of days that have passed since 12/30/1899. The fractional part of a TDateTime value is the time of day.
Following are some examples of TDateTime values and their corresponding dates and times:
0 12/30/1899 12:00 am
2.75 1/1/1900 6:00 pm
-1.25 12/29/1899 6:00 am
35065 1/1/1996 12:00 am
内存中TDateTime类型存储的实际值是double类型的,整数部分是当前日期自12/30/1899 12:00 am起经过的天数,大于为正,小于为负,小数部分是剩下的部分按豪秒计算转换得来的。上边是帮助中的例子,但实际把TDateTime类型转化成double后小数精度要高得多不止两位,好像是6位吧。