第一行 Ttime ?=now的值 ?timetostr時間顯示為15:08:50 ?雙浮點數double類型，8字節

? 小數點部分記錄時間 0.6311428009 *24=15.1474272216 ?取整為15， ?0.1474272216*60=8.845633296 取整8為分，

? ? ?0.845633296*60=50.73799776 取整為50為為秒，0.73799776*1000=737為毫秒。

? 這是時間的計算方法。

? ? 如果復制time，整數部分就為0了。

第三行 tDatetime ?now的，Datetimetostr時間顯示為2016-10-08 15:09:55，?雙浮點數double類型，8字節

? 小數點以后的表示的時間，如上計算。

? 整數部分，表示的日期。自1899-12-30后的天數。

Tdate就是去掉小數部分的內容

網友:1：double數據類型是計算機四種基本類型之一，另外三個是：int，char，float 基本在每一種編程語言當中都有的實現。 2：在delphi當中double也是64位的。 3：c＋＋當中double也是64位， 4：兩種編程語言的double范圍都是一樣的

In Delphi, TDateTime is a type that maps to a Double. In C++, the TDateTime class corresponds to the Delphi TDateTime type. ?

The integral part of a Delphi TDateTime value is the number of days that have passed since 12/30/1899. The fractional part of the TDateTime value is fraction of a 24 hour day that has elapsed. ?

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 ?

To find the fractional number of days between two dates, simply subtract the two values, unless one of the TDateTime values is negative. Similarly, to increment a date and time value by a certain fractional number of days, add the fractional number to the date and time value if the TDateTime value is positive. ?

When working with negative TDateTime values, computations must handle time portion separately. The fractional part reflects the fraction of a 24-hour day without regard to the sign of the TDateTime value. For example, 6:00 am on 12/29/1899 is –1.25, not –1 + 0.25, which would be –0.75. There are no TDateTime values between –1 and 0.

Note:?Delphi 1.0 calculated the date from year 1 instead of from 1899. To convert a Delphi 1.0 date to a TDateTime value in later versions of the Delphi language, subtract 693594.0 from the Delphi 1.0 date. ?

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