To change time on a Casio calculator watch, one needs to have knowledge of the watch’s structure and clock mechanics. Firstly, one needs to identify the type of watch that needs to be changed. There are different types of Casio calculators, such as the C-500, C-750, and C-1000. Each of these watches has its own unique structure and clock mechanism. The watch should be returned to the retailer or service center for repair. The repair process can vary depending on the model and make of watch. For example, the C-500 watch has a switch to change the time, while the C-750 watch has a gear that can be used to change the time. To change the time on the C-1000 watch, one needs to have a spare winding in the watch. To do this, one needs to turn the watch over to change the winding. It is important to remember that changing the time on a watch requires knowledge of the watch’s structure and clock mechanics.