I get the following error when compiling a C FLL with MSVC 6.0 SP4, any ideas?

Linking...
Creating library time_ttot___Win32_Debug/time_ttot.lib and object time_ttot___Win32_Debug/time_ttot.exp
time_ttot.obj : error LNK2001: unresolved external symbol @_RetDateTimeStr@4
time_ttot___Win32_Debug/time_ttot.dll : fatal error LNK1120: 1 unresolved externals