This is a video from Real English.com. In this video people talk about their birthdays and other special occasions. Listen. can you hear the dates? Listen and practice saying the dates.
Practice pronouncing "th" in dates, for example: fourth, fifth, sixth, and so on. Look at the picture below to help you. The picture below shows the shape of a mouth making the "th" sound. Look at the tongue. It's between the teeth.
Click the image in order to make it bigger
Many student make the "s" sound instead of the "th" sound. For example, some students say, "tense" (緊張した)when they want to say "tenth" (10th).
The picture below shows the shape of the mouth making the "s" sound. You can't see the tongue.
Practice the dates that you hear on the video using a mirror. Then you can see if you are making your mouth the correct shape.