Amlich.jad, follow the installation guide of your phone to transfer those files to your phone.
You may need to install additional fonts to display Vietnamese characters correctly. Consult your phone's manual or search the internet for details. For Nokia phones, download font Tahoma, extract and copy the file
Currently selected day is shown in a box. Starting day of lunar month (ngày mùng 1 tháng âm lịch) is underlined.
Use LEFT, RIGHT (on many phones: key 4 and 6) to go 1 day backwards/forwards. Use UP, DOWN (the UP/DOWN buttons or keys 2 and 8 on many phones) to go 1 week backwards or forwards.
To see details of currently selected day, push the FIRE button (usually key 5 on mobile phones) or activate command "View current".
To select another month, push the FIRE button or activate the command "View current". A screen will appear that allows you to enter another date.
To view help, activate the "Help" command
If your device supports pointer, you can navigate around with it. Tap a day to select it. Tap again to view its details. Tap the button "<<", "<", ">", ">>" to move 1 month or 1 year.