Question

VBScript represents dates internally as a double, days since “year 0” in the part to the left of the decimal point and the milliseconds since midnight for the current day to the right of the decimal. “Year 0” seems to be 1899 if

WScript.Echo Year(CDate(0))

can be trusted.

JScript on the other hand starts with a “year 0” of 1970 and represents time as the total milliseconds from then until now.

Can someone point me to code that makes possible conversion of JScript dates to VBScript dates and back again along these lines, of using the underlying Double or Long format of the date?

Answer 1

Generate date using timestamp and convert into double.

Function CurrentTZOffset()
    With CreateObject("WScript.Shell") 
        CurrentTZOffset = - .RegRead( _ 
        "HKLM\System\CurrentControlSet\Control\TimeZoneInformation\ActiveTimeBias")
    End With
End Function

Dim dblVbEpoch
    dblVbEpoch = CDbl(DateAdd("s", 1336708766790 / 1000, #1970/1/1#))

WScript.Echo "VB Epoch :", dblVbEpoch
WScript.Echo "VB Date (GMT):", CDate(dblVbEpoch)
WScript.Echo "VB Date (LOCAL):", DateAdd("n", CurrentTZOffset(), CDate(dblVbEpoch))
WScript.Echo "JS Epoch From VB Epoch:", DateDiff("s", #1970/1/1#, CDate(dblVbEpoch)) * 1000