问一个关于TTime的问题 ( 积分: 50 )

time1,time2:TTime;
time1 := time();
time2 := RzDateTimePicker1.Time;

我本想通过CompareTime(time1,time2) = EqualsValue来判断两个值相等，但发现这么也不行，后来debug发现 time1 大约是0.xxxxxxxxx，而time2确是8xxxxxx.xxxxxx，这是为什么？

time1,time2:TTime;
time1 := time();
time2 := RzDateTimePicker1.Time;

我本想通过CompareTime(time1,time2) = EqualsValue来判断两个值相等，但发现这么也不行，后来debug发现 time1 大约是0.xxxxxxxxx，而time2确是8xxxxxx.xxxxxx，这是为什么？

TDate = type TDateTime;

TTime = type TDateTime;

TDateTime = type Double;

uses DateUtils



function DateOf(const AValue: TDateTime): TDateTime;
function TimeOf(const AValue: TDateTime): TDateTime;

{ Misc functions }

function IsInLeapYear(const AValue: TDateTime): Boolean;
function IsPM(const AValue: TDateTime): Boolean;
function IsValidDate(const AYear, AMonth, ADay: Word): Boolean;
function IsValidTime(const AHour, AMinute, ASecond, AMilliSecond: Word): Boolean;
function IsValidDateTime(const AYear, AMonth, ADay, AHour, AMinute, ASecond,
AMilliSecond: Word): Boolean;
function IsValidDateDay(const AYear, ADayOfYear: Word): Boolean;
function IsValidDateWeek(const AYear, AWeekOfYear, {ISO 8601}
ADayOfWeek: Word): Boolean;
function IsValidDateMonthWeek(const AYear, AMonth, AWeekOfMonth, {ISO 8601x}
ADayOfWeek: Word): Boolean;
function WeeksInYear(const AValue: TDateTime): Word
{ISO 8601}
function WeeksInAYear(const AYear: Word): Word
{ISO 8601}
function DaysInYear(const AValue: TDateTime): Word;
function DaysInAYear(const AYear: Word): Word;
function DaysInMonth(const AValue: TDateTime): Word;
function DaysInAMonth(const AYear, AMonth: Word): Word;
function Today: TDateTime;
function Yesterday: TDateTime;
function Tomorrow: TDateTime;
function IsToday(const AValue: TDateTime): Boolean;
function IsSameDay(const AValue, ABasis: TDateTime): Boolean;

{ Pick-a-field functions }

function YearOf(const AValue: TDateTime): Word;
function MonthOf(const AValue: TDateTime): Word;
function WeekOf(const AValue: TDateTime): Word
{ISO 8601}
function DayOf(const AValue: TDateTime): Word;
function HourOf(const AValue: TDateTime): Word;
function MinuteOf(const AValue: TDateTime): Word;
function SecondOf(const AValue: TDateTime): Word;
function MilliSecondOf(const AValue: TDateTime): Word;

{ Start/End functions }

function StartOfTheYear(const AValue: TDateTime): TDateTime;
function EndOfTheYear(const AValue: TDateTime): TDateTime;
function StartOfAYear(const AYear: Word): TDateTime;
function EndOfAYear(const AYear: Word): TDateTime;

function StartOfTheMonth(const AValue: TDateTime): TDateTime;
function EndOfTheMonth(const AValue: TDateTime): TDateTime;
function StartOfAMonth(const AYear, AMonth: Word): TDateTime;
function EndOfAMonth(const AYear, AMonth: Word): TDateTime;

function StartOfTheWeek(const AValue: TDateTime): TDateTime
{ISO 8601}
function EndOfTheWeek(const AValue: TDateTime): TDateTime
{ISO 8601}
function StartOfAWeek(const AYear, AWeekOfYear: Word
{ISO 8601}
const ADayOfWeek: Word = 1): TDateTime;
function EndOfAWeek(const AYear, AWeekOfYear: Word
{ISO 8601}
const ADayOfWeek: Word = 7): TDateTime;

function StartOfTheDay(const AValue: TDateTime): TDateTime;
function EndOfTheDay(const AValue: TDateTime): TDateTime;
function StartOfADay(const AYear, AMonth, ADay: Word): TDateTime
overload;
function EndOfADay(const AYear, AMonth, ADay: Word): TDateTime
overload;
function StartOfADay(const AYear, ADayOfYear: Word): TDateTime
overload;
function EndOfADay(const AYear, ADayOfYear: Word): TDateTime
overload;

{ This of that functions }

function MonthOfTheYear(const AValue: TDateTime): Word;
function WeekOfTheYear(const AValue: TDateTime): Word
overload
{ISO 8601}
function WeekOfTheYear(const AValue: TDateTime
{ISO 8601}
var AYear: Word): Word
overload;
function DayOfTheYear(const AValue: TDateTime): Word;
function HourOfTheYear(const AValue: TDateTime): Word;
function MinuteOfTheYear(const AValue: TDateTime): LongWord;
function SecondOfTheYear(const AValue: TDateTime): LongWord;
function MilliSecondOfTheYear(const AValue: TDateTime): Int64;

function WeekOfTheMonth(const AValue: TDateTime): Word
overload
{ISO 8601x}
function WeekOfTheMonth(const AValue: TDateTime
var AYear, {ISO 8601x}
AMonth: Word): Word
overload;
function DayOfTheMonth(const AValue: TDateTime): Word;
function HourOfTheMonth(const AValue: TDateTime): Word;
function MinuteOfTheMonth(const AValue: TDateTime): Word;
function SecondOfTheMonth(const AValue: TDateTime): LongWord;
function MilliSecondOfTheMonth(const AValue: TDateTime): LongWord;

function DayOfTheWeek(const AValue: TDateTime): Word
{ISO 8601}
function HourOfTheWeek(const AValue: TDateTime): Word
{ISO 8601}
function MinuteOfTheWeek(const AValue: TDateTime): Word
{ISO 8601}
function SecondOfTheWeek(const AValue: TDateTime): LongWord
{ISO 8601}
function MilliSecondOfTheWeek(const AValue: TDateTime): LongWord
{ISO 8601}

function HourOfTheDay(const AValue: TDateTime): Word;
function MinuteOfTheDay(const AValue: TDateTime): Word;
function SecondOfTheDay(const AValue: TDateTime): LongWord;
function MilliSecondOfTheDay(const AValue: TDateTime): LongWord;

function MinuteOfTheHour(const AValue: TDateTime): Word;
function SecondOfTheHour(const AValue: TDateTime): Word;
function MilliSecondOfTheHour(const AValue: TDateTime): LongWord;

function SecondOfTheMinute(const AValue: TDateTime): Word;
function MilliSecondOfTheMinute(const AValue: TDateTime): LongWord;

function MilliSecondOfTheSecond(const AValue: TDateTime): Word;

{ Range checking functions }

function WithinPastYears(const ANow, AThen: TDateTime;
const AYears: Integer): Boolean;
function WithinPastMonths(const ANow, AThen: TDateTime;
const AMonths: Integer): Boolean;
function WithinPastWeeks(const ANow, AThen: TDateTime;
const AWeeks: Integer): Boolean;
function WithinPastDays(const ANow, AThen: TDateTime;
const ADays: Integer): Boolean;
function WithinPastHours(const ANow, AThen: TDateTime;
const AHours: Int64): Boolean;
function WithinPastMinutes(const ANow, AThen: TDateTime;
const AMinutes: Int64): Boolean;
function WithinPastSeconds(const ANow, AThen: TDateTime;
const ASeconds: Int64): Boolean;
function WithinPastMilliSeconds(const ANow, AThen: TDateTime;
const AMilliSeconds: Int64): Boolean;

{ Range query functions }

function YearsBetween(const ANow, AThen: TDateTime): Integer;
function MonthsBetween(const ANow, AThen: TDateTime): Integer;
function WeeksBetween(const ANow, AThen: TDateTime): Integer;
function DaysBetween(const ANow, AThen: TDateTime): Integer;
function HoursBetween(const ANow, AThen: TDateTime): Int64;
function MinutesBetween(const ANow, AThen: TDateTime): Int64;
function SecondsBetween(const ANow, AThen: TDateTime): Int64;
function MilliSecondsBetween(const ANow, AThen: TDateTime): Int64;

{ Range spanning functions }
{ YearSpan and MonthSpan are approximates, not exact but pretty darn close }
function YearSpan(const ANow, AThen: TDateTime): Double;
function MonthSpan(const ANow, AThen: TDateTime): Double;
function WeekSpan(const ANow, AThen: TDateTime): Double;
function DaySpan(const ANow, AThen: TDateTime): Double;
function HourSpan(const ANow, AThen: TDateTime): Double;
function MinuteSpan(const ANow, AThen: TDateTime): Double;
function SecondSpan(const ANow, AThen: TDateTime): Double;
function MilliSecondSpan(const ANow, AThen: TDateTime): Double;

获取当前系统时间利用函数GetSystemTime比较方便而且灵活，Time都只能获得精确到秒的时间(即两位数)，为了得到更精确的毫秒级时间，可以使用API函数GetSystemTime，它对应的TSystemTime类型的定义为：

TSystemTime = record

wYear: Word;

wMonth: Word;

wDayOfWeek: Word;

wDay: Word;

wHour: Word;

wMinute: Word;

wSecond: Word;

wMilliseconds: Word;

RzDateTimePicker1.Time 返回的是一个带日期的时间
而time（）之返回时间
正确得方法是
CompareTime(Frac(time1),Frac(time2));