Classic Asp cookie expires date does not always get set - vbscript

Question

I am trying to set cookie with addheader -method in Classic Asp which is the only way of adding among other things HttpOnly and Secure -flags to cookies. All work with the below code - but there is one exception and its is the expiration date/time.
<%
Response.AddHeader "Set-Cookie", "testCookie=2000; path=/;HttpOnly;Secure;expires=" & dateAdd("d", 365, Now()) & ";samesite=Strict;HostOnly"
%>
However, it seems to be browser-related issue. In firefox I can see in the Storage tab of developer tools that expiration time is set. But in Chrome it always stays as the default which is the expiration with the end of session. This same issue is with the Edge too.
Has anyone any experience with this issue?

Answer 1

The expected date format is documented here. You need to produce expiration date in that manner.
In Classic ASP, you can use server-side JavaScript to produce such dates easily.
<!--#include file="HTTPDate.asp"-->
<%
Response.AddHeader "Set-Cookie", "testCookie=2000; path=/;HttpOnly;Secure;expires=" & HTTPDate(DateAdd("d", 365, Now())) & ";samesite=Strict;HostOnly"
%>
HTTPDate.asp
<script language="javascript" runat="server">
function HTTPDate(vbsDate){
return (new Date(vbsDate)).toGMTString().replace(/UTC/, "GMT");
}
</script>
Edit: Pure VBScript solution added.
<%
Function CurrentTZO()
With CreateObject("WScript.Shell")
CurrentTZO = .RegRead( _
"HKLM\System\CurrentControlSet\Control\TimeZoneInformation\ActiveTimeBias")
End With
End Function
Function Pad(text)
Pad = Right("00" & text, 2)
End Function
Function HTTPDate(ByVal localDate)
localDate = DateAdd("n", CurrentTZO(), localDate)
' WeekdayName and MonthName functions relies on locale
' need to produce day and month name abbreviations in en-US locale
Dim locale : locale = SetLocale("en-US")
Dim out(5)
out(0) = WeekdayName(Weekday(localDate), True) & ","
out(1) = Pad(Day(localDate))
out(2) = MonthName(Month(localDate), True)
out(3) = Year(localDate)
out(4) = Join(Array(Pad(Hour(localDate)), Pad(Minute(localDate)), Pad(Second(localDate))), ":")
out(5) = "GMT"
SetLocale locale ' set original locale back
HTTPDate = Join(out, " ")
End Function
Response.AddHeader "Set-Cookie", "testCookie=2000; path=/;HttpOnly;Secure;expires=" & HTTPDate(DateAdd("d", 365, Now())) & ";samesite=Strict;HostOnly"
%>

Answer 2

In addition to the accepted solution of Kul-Tigin I want to add also a vbscript solution for those who are missing that too.
<%
Response.AddHeader "Set-Cookie", "testCookie=2000; path=/;HttpOnly;Secure;expires=" & (New UTC).toUTCString(500,"d") & ";samesite=Strict;HostOnly;"
Class UTC
Public Function toUTCString(ByVal offSet, ByVal offsetType)
' ***********************************
' Converts vbScript datetime format to
' Universal datetime string format:
' Tue, 16 Feb 2021 13:39:24 GMT
'************************************
Dim dt: dt = dateAdd(offsetType, offSet, UTCDate(Now()))
Dim tdParts: tdParts = Split(dt, " ")
Dim tPart: tPart = CDate(tdParts(1) & " " & tdParts(2))
Dim dPart: dPart = CDate(tdParts(0))
Dim timeTo24: timeTo24 = _
Right("0" & Hour(tPart), 2) & ":" & _
Right("0" & Minute(tPart), 2) & ":" & _
Right("0" & Second(tPart), 2)
toUTCString = WeekdayName(Weekday(dPart), True) & ", " & _
Day(dPart) & " " & _
MonthName(Month(dPart), True) & " " & _
Year(dPart) & " " & _
timeTo24 & " GMT"
End Function
Public Function UTCDate(ByVal dtDate)
If Not IsDate(dtDate) Then Err.Raise 5
dtDate = CDate(dtDate)
Dim ZoneBias: ZoneBias = TimeZoneBias()
If IsPDT(Now) <> IsPDT(dtDate) Then
ZoneBias = ZoneBias - 60
End If
UTCDate = DateAdd("n", ZoneBias, dtDate)
End Function
Private Function IsPDT(ByVal dtDate)
If Not IsDate(dtDate) Then Err.Raise 5
dtDate = CDate(dtDate)
Dim pdtLow, pdtUpr, nDaysBack
pdtLow = DateSerial(Year(dtDate), 3, 31)
pdtUpr = DateSerial(Year(dtDate), 10, 31)
pdtLow = DateAdd("h", 2, pdtLow)
pdtUpr = DateAdd("h", 2, pdtUpr)
nDaysBack = Weekday(pdtLow) - 1
If nDaysBack <> 0 Then
pdtLow = DateAdd("d", -nDaysBack, pdtLow)
End If
nDaysBack = Weekday(pdtUpr) - 1
If nDaysBack <> 0 Then
pdtUpr = DateAdd("d", -nDaysBack, pdtUpr)
End If
IsPDT = (dtDate >= pdtLow And dtDate <= pdtUpr)
End Function
Private Function TimeZoneBias()
Dim LTZone
With GetObject("winmgmts:" & _
"{impersonationLevel=impersonate}!\\.\root\cimv2")
For Each LTZone In .ExecQuery(_
"Select * From Win32_ComputerSystem")
TimeZoneBias = LTZone.CurrentTimeZone
Next
End With
TimeZoneBias = TimeZoneBias * -1
End Function
End Class
%>