Thaihealthnews 2.02 modules need calendar function when you compile PHP --enable-calendar ,which is default setting in new redhat, ensim , or other control panel., however if you upgrade or compile PHP , do not forget , or you will get error gregoriantojd function !

see here 

http://www.php.net/manual/en/ref.calendar.php
so may you recompile php with it again or use other script to change date to string

remove old PHP

#rpm -e php-devel

#rpm -e php-mysql

#rpm -e php

download package of PHP to some directory

# tar xvfz php-4.3.3.tar.gz
# cd php-4.3.3
# ./configure --prefix=/usr --with-apxs=/usr/local/apache2/bin/apxs --enable-ftp --with-zlib-dir=/usr --with-openssl --with-mysql=/usr/local/mysql --with-mysql-sock=/tmp/mysql.sock --enable-force-cgi-redirect --enable-pcntl --enable-shmop --enable-xml --with-gd --with-bz2 --with-ttf --with-png --with-jpeg-dir=/usr --with-png-dir=/usr --with-freetype-dir=/usr --with-expat-dir=/usr --with-config-file-path=/etc --with-gmp --enable-socket --enable-force-cgi-redirect --with-pear=/usr/share/pear --with-ldap=shared --with-pspell --disable-debug --disable-rpath --disable-posix --enable-pic --enable-safe-mode --enable-magic-quotes --enable-discard-path --enable-bcmath --enable-dio --enable-gd-native-ttf --enable-sysvsem=shared --enable-sysvshm=shared --enable-track-vars --enable-memory-limit --enable-inline-optimization --enable-calendar

**note***all above configure script should be type continue in one line, do not enter before end*****
# make
# make install
# make clean
and can check by phpinfo() function