need help about compile source for v21.2

[Hostolor]

IDE Version: Visual Studio 2019
Error: "FLDateTime": Not A Class Or Namespace name
File: _CommonDefine\FLTm.cpp,

BOOL				FLLessThanTimeOnly( const FLDateTime::FLTm & src, const FLDateTime::FLTm & dst )
{
	return ( src.value << 47 ) < ( dst.value << 47 );
}

BOOL FLDateTime::FLEqualTimeOnly( const FLDateTime::FLTm & src, const FLDateTime::FLTm & dst )
{
	return ( src.value << 47 ) == ( dst.value << 47 );
}

anybody know how to fix this ? thanks.

[MentaL]