Make file not working for boost

[drubashir]

Hi , i am using the following structure for make file

OBJECTS := time.o
PROGRAM := time
CPPFLAGS += -Iusr/include/boost_1_49_0 -Lusr/include/boost_1_49_0/stage/lib
CXXFLAGS := -Wall -ggdb3
LDFLAGS += -lboost_date_time
$(PROGRAM) : $(OBJECTS)
g++ -o time time.cpp

clean :
rm $(PROGRAM) $(OBJECTS)

but when i enter make, it gives me lots of errors including

undefined reference to `boost::gregorian::greg_month::as_short_string() const'
time.cpp:(.text._ZN5boost9date_time15month_formatterINS_9gregorian10greg_monthENS0_13simple_formatIcEEcE12format_monthERKS3_RSo[boost::date_time::month_formatter<boost::gregorian::greg_month, boost::date_time::simple_format<char>, char>::format_month(boost::gregorian::greg_month const&, std::basic_ostream<char, std::char_traits<char> >&)]+0x56): undefined reference to `boost::gregorian::greg_month::as_long_string() const'
collect2: ld returned 1 exit status

When i use g++ -Wall -Iusr/include/boost_1_49_0 -Lusr/include/boost_1_49_0/stage/lib -o time time.cpp -lboost_date_time

the code compiles fine so somthing is not write with my makefile , please help (NOTE: i tried placing the -L <directory> flag in the LDFLAG variable but that didnt work either)