Get Unix time milliseconds

Question

In Java to get system time in milliseconds I use:

 new date().gettime()

It is possible to get the same result in milliseconds using Excel VBA?

Answer 1

SUMMARY: For best results, use GetSystemTime.

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The Excel worksheet function Now() has relatively good precision, roughly down to 10 ms. But to call it you have to use a worksheet formula.

To correctly get the milliseconds value, you should avoid the VBA Now() function. Its precision is roughly 1 second.

The VBA Timer() function returns a single with a precision of roughly 5 milliseconds. But you have to use Now() to get the date part. This might cause a slight problem if Now() is called before midnight and Timer() is called after midnight (this is probably a rare situation and not an issue for most people).

The Windows API function GetSystemTime has true millisecond precision. You can use the values in the SYSTEMTIME structure to create an Excel double that has the correct millisecond precision. GetSystemTime returns the UTC time so if you want the date in POSIX format, you can subtract the UNIX epoch (1 January 1970 UTC), which is 25569 in Excel date format (disregarding leap seconds).

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The code below compares the precision of each method:

Option Explicit

Private Type SYSTEMTIME
    wYear As Integer
    wMonth As Integer
    wDayOfWeek As Integer
    wDay As Integer
    wHour As Integer
    wMinute As Integer
    wSecond As Integer
    wMilliseconds As Integer
End Type

' Retrieves the current system date and time in Coordinated Universal Time (UTC) format.
' To retrieve the current system date and time in local time, use the GetLocalTime function.
Private Declare PtrSafe Sub GetSystemTime Lib "kernel32" (lpSystemTime As SYSTEMTIME)

Function Now_System() As Double
    Dim st As SYSTEMTIME
    GetSystemTime st
    Now_System = DateSerial(st.wYear, st.wMonth, st.wDay) + _
        TimeSerial(st.wHour, st.wMinute, st.wSecond) + _
        st.wMilliseconds / 86400000#
End Function

Function Now_Timer() As Double
    Now_Timer = CDbl(Int(Now)) + CDbl(Timer() / 86400#)
End Function


Sub CompareCurrentTimeFunctions()
    ' Compare precision of different methods to get current time.
    Me.Range("A1:D1000").NumberFormat = "yyyy/mm/dd h:mm:ss.000"

    Dim d As Double
    Dim i As Long
    For i = 2 To 1000
        ' 1) Excel NOW() formula returns same value until delay of ~10 milliseconds. (local time)
        Me.Cells(1, 1).Formula = "=Now()"
        d = Me.Cells(1, 1)
        Me.Cells(i, 1) = d

        ' 2) VBA Now() returns same value until delay of ~1 second. (local time)
        d = Now
        Me.Cells(i, 2) = d

        ' 3) VBA Timer returns same value until delay of ~5 milliseconds. (local time)
        Me.Cells(i, 3) = Now_Timer
        
        ' 4) System time is precise down to 1 millisecond. (UTC)
        Me.Cells(i, 4) = Now_System
    Next i
End Sub