DaysBetween function Returns the number of whole days between two specified TDateTime values.UnitDateUtilsCategorydatetime routinesDelphi syntax:function DaysBetween(const ANow, AThen: TDateTime): Integer;C++ syntax:extern PACKAGE int __fastcall DaysBetween(const System::TDateTime ANow, const System::TDateTime AThen);DescriptionCall DaysBetween to obtain the difference, in days, between two TDateTime values.DaysBetween counts only whole days. Thus, DaysBetween reports the difference between Dec 31, 1999 11:59 PM and Jan 1, 2000 11:58 PM as 0 because the difference is one minute short of an entire day.
DaySpan functionReturns the number of days (including fractional days) between two specified TDateTime values.UnitDateUtilsCategorydatetime routinesDelphi syntax:function DaySpan(const ANow, AThen: TDateTime): Double;C++ syntax:extern PACKAGE double __fastcall DaySpan(const System::TDateTime ANow, const System::TDateTime AThen);DescriptionCall DaySpan to obtain the difference, in days, between two TDateTime values. Unlike the DaysBetween function, which only counts whole days, DaySpan reports incomplete days as a fraction of an entire day.
前者返回整数，后者返回小数，精度高
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Returns the number of whole days between two specified TDateTime values.UnitDateUtilsCategorydatetime routinesDelphi syntax:function DaysBetween(const ANow, AThen: TDateTime): Integer;C++ syntax:extern PACKAGE int __fastcall DaysBetween(const System::TDateTime ANow, const System::TDateTime AThen);DescriptionCall DaysBetween to obtain the difference, in days, between two TDateTime values.DaysBetween counts only whole days. Thus, DaysBetween reports the difference between Dec 31, 1999 11:59 PM and Jan 1, 2000 11:58 PM as 0 because the difference is one minute short of an entire day.