我需要通过AJAX发送一个delphi服务器的日期，该服务器接受float格式的日期并设置一个TDateTime属性。
例如。
var
date: TDateTime;
begin
date := StrToFloat(Request.QueryFields.Values['date']);
end;
Delphi TDateTime从1989年12月30日开始，我已经测试过：
var
date: TDateTime;
begin
date := StrToFloat('0');
ShowMessage( DateTimeToStr(date) ); // show: 30/12/1899
end;
JavaScript日期从Unix时代开始，我已经测试过：
console.log(new Date(0)); // Thu Jan 01 1970 01:00:00 GMT+0100
一个简单的转换似乎会减去差异，但不起作用，例如：
// javascipt
var delphiTime = (new Date("07-24-2019") - new Date("12-30-1899")) / 1000;
console.log(delphiTime ); // 3773084400
// delphi
ShowMessage( DateTimeToStr(3773084400) ); // show 00/00/00
奇怪的事实是，在delphi上，
Now是43670.654378：ShowMessage( FloatToStr(Now) ); // 43670.654378
在delphi中0是1899，43670是2019 ...
Delphi中的日期格式如何工作以及如何使用数学将Unix日期转换为Delphi日期？
旁注：我无法修改服务器，我需要使用JavaScript解决客户端问题
更新：
在Delphi中，浮点值= 1将是31.12.1899，2 = 01.01.1900，依此类推。每个单元似乎一天。
function jsDateToDelphiDate(date){
const seconds = (new Date(date).getTime() - new Date("12-30-1899").getTime()) / 1000;
const days = seconds / 60 / 60 / 24;
return days;
}
console.log(jsDateToDelphiDate(new Date("07-24-2019 16:00:00"))); // 43670.625
delphi上的
43670.625是23/07/2019 15:00。为什么我会损失1个小时？
最佳答案
如何在Delphi中使用日期格式
这在Embarcadero's DocWiki上有完整记录：
System.TDateTime
TDateTime类继承了一个val数据成员（声明为double成员），该成员保留日期时间值。 TDateTime值的整数部分是自1899年12月30日以来经过的天数。TDateTime值的小数部分是一天中的时间。
...
下表显示了TDateTime值及其对应的日期和时间的示例：
Value Description 0 December 30, 1899; 12:00 A.M. 2.75 January 1, 1900; 6:00 P.M. -1.25 December 29, 1899; 6:00 A.M. 35065 January 1, 1996; 12:00 A.M.
A Unix date/time is represented as the number of seconds since January 1 1970 00:00:00 UTC. Delphi has a UnixDateDelta constant in the SysUtils unit which is defined as 25569, the number of days from December 31 1899 to January 1 1970. So, a TDateTime value of 25569.0 exactly represents January 1 1970 00:00:00 (UTC vs local is up to you to decide when creating a TDateTime). You can then add seconds to that value to get the final TDateTime value for any Unix date/time.
In a TDateTime, you can add whole days to the integral portion (ie, Unix + 1 day = 25569.0 + 1 = 25570.0), but adding seconds within a day is slightly more work, as seconds are not represented as-is in TDateTime, as you can see in the table above. 0.25 is 6:00 AM (21600 seconds after midnight) and 0.75 is 6:00 PM (64800 seconds after midnight). So seconds are represented in TDateTime as a fraction with 86400 (the number of seconds in a day) as the denominator.
A JavaScript Date object is represented as the number of milliseconds since midnight on January 1 1970. You can divide a Date value by 1000 to get whole seconds, and divide that value by 86400 to get whole days and fractional seconds, which you can then add to 25569.0 to produce a TDateTime value.
function jsDateToDelphiDate(dateToConvert){
const UnixDateDelta = 25569.0;
const SecsPerDay = 86400;
const MSecsPerSec = 1000;
var UnixSeconds = dateToConvert.getTime() / MSecsPerSec; // 1563984000
var SecsToAdd = UnixSeconds / SecsPerDay; // 18101.666666666668
return UnixDateDelta + SecsToAdd;
}
// don't forget to force UTC, or else the Date value
// will be skewed by the local timezone offset...
console.log(jsDateToDelphiDate(new Date("2019-07-24T16:00:00Z"))); // 43670.66666666667
console.log(jsDateToDelphiDate(new Date(Date.UTC(2019, 6, 24, 16, 0, 0)))); // 43670.66666666667
Delphi在
UnixToDateTime()单元中具有DateUtils函数，该函数可以为您执行此计算。因此，如果可以更改AJAX代码以将Unix时间戳原样传递给Delphi，则可以让Delphi计算合适的TDateTime。注意，在此示例中，结果
TDateTime值以UTC为单位。通过AJAX将值传输到Delphi后，如果您的Delphi代码在本地时间需要TDateTime，这是一种基于本地计算机的时区偏移量（以分钟为单位）调整TDateTime的简单计算，您可以使用平台API来获取，例如Windows上的GetTimeZoneInformation()等。Delphi在IncMinute()单元中具有DateUtils函数，您可以使用该函数进行调整。关于javascript - JavaScript日期为Delphi TDateTime，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/57184472/