Lunar and Tide Calendar Postcard

This postcard is a dual-use calendar. On one side you will find a lunar calendar that allows you to find out what was, or what will be the phase of the moon on a certain date. It is based on the epact (the age of the moon). On the other side a calendar of tides, with which you can find out what time it will produce both high and low waters of a port. Here we present it as a postcard. It is functional, with rotating disc and beautifully decorated.