Patent GB-577082-A (GB)
Abstract: 577,082. Calendars. HOWLETT, F. C. Feb. 21, 1944, No. 3145. [Class 106 (iv)] In a perpetual calendar having a frame carrying a movable month-year card indicating the months spaced according to the order in which their first days fall on consecutive days of the week, and the years arranged in rows of similar spacing and order, a second movable card having the day numbers arranged thereon in known septiform spacing and means for indicating a particular month on the first card, and a stationary member indicating the seven day names spaced to correspond with the day numbers on the second card, to ensure that the second card always shows the correct number of days in the month, the day numbers end at 28 followed by a window corresponding in size to three numbers, and mounted behind the second card is a further movable card which can be arranged to mask all the months except one, and to show through the window the number of days additional to 28 appropriate to that month, and to avoid having a separate month-year card for leap years, the leap year data is interspersed in rows with that for normal years, and a movable masking grid is provided so that data either for a leap year or for a normal year is visible, but not both. In one form the calendar comprises a frame G, apertured back F, vertically movable month-year card C having 13 rows of months on the front, arranged in order of the week days on which the first of each month falls, which may be alternated with a further 13 rows as shown in Fig. 3 to provide for leap years, and 7 rows of years on the back having the same spacing as the rows of months, each row indicating all the years during the period in question whose first day falls on a particular week day. The card B acts as a masking grid, whereby the months on card C corresponding to a normal year or to a leap year are visible, but not both. The card A has the day numbers arranged in 13 lines in known manner and terminating at 28 and two windows A<1> and A<2>. Behind card A is secured a square card 4 on which is rotatably mounted a disc D with a portion cut away from its periphery at D, so that it is capable of limited rotation about the stop 4a, and having windows D<1>-D<6>. The front consists of a card E carrying the day numbers and having two apertures E<1>, E<2>. In use, the card C is moved vertically until the row on the back thereof containing the year in question is opposite a datum line on the member F, by means of a knob on the spindle 2 the disc D is turned until the slit D<1> is aligned with the slit A<3>, whereupon the card A complete with disc D is adjusted vertically until the row of months visible through the slits contains the month in question, the knob is then rotated until only that month is visible through one of the slits D<2>-D<6>, whereby the appropriate numerical addition to the 28 days is visible through one of the windows A<1> or A<2>. Instead of the rotatable disc D, a sliding masking card can be used, such card being slid by a tongue projecting through a slot in the card A, whereby the necessary vertical adjustment of the card A may also be made ; a vertically adjustable cursor may be used in conjunction, to indicate the particular month.