I have a makefile and two simple VB.NET files. The problem is that nmake
doesn't seem to respect the last modified timestamp of the file. Every time
I run it, it recompiles the exe even if the source is up to date.

the file names, nmake respects the last modified timestamp.

Is this a bug in Microsoft's nmake?

#-- MAKEFILE --

_SYSTEM_IMPORTS = /r:System.dll

EXEs = ShowHello ShowTime

all : $(EXEs)

 vbc /t:exe $? $(_SYSTEM_IMPORTS)

clean :

#-- END MAKEFILE --

'-- ShowHello.vb --

Option Explicit On
Option Strict On

Imports System
Module m
    Public Sub Main()
        Console.WriteLine("Hello World")
    End Sub
End Module

'-- End ShowHello.vb --

'-- ShowTime.vb --
Option Explicit On
Option Strict On
Imports System
Imports System.DateTime
Module m
    Public Sub Main()
        Console.WriteLine(Now)
    End Sub
End Module
'-- End ShowTime.vb --