Abstract: A slide rule-calendar having a fixed part, two sliding parts and a cursor. On the lower portion of the fixed part, the thirty-one days of the longest month are indicated horizontally. The twelve months of the year are indicated on the left vertical portion of the fixed part and also on the cursor.By positioning the two sliding parts on predetermined parameters shown on the top and bottom left portion of the fixed part which parameters correspond as a pair to a series of equivalent years and by moving the cursor to the desired day, all the days of the week of the equivalent past and future years corresponding to said pair of parameters can be determined, with only one positioning of the two sliding parts.