This line represents the beginning of a new year for the years block, the first day of a new month, or a Monday for the weeks

Usually, our periods of life are not the same as the calendar year or months. However, if our birthday falls on the first day of the month, specifically in January, and it is a Monday, only then our period of life aligns exactly with the calendar periods. To display the calendar period on your calendar, you can enable the new calendar period setting

In the example below, you can see the new calendar period line for July, which is located in the center of the block.