To ensure optimum performance you should change your filter cartridge on a regular basis. The BRITA "Calendar" as featured on the Space Saver Filter Jug, is a manual cartridge exchange indicator. It's easy to use. Using the BRITA Calendar you can set the date for the next filter cartridge exchange. The left-hand field shows the day, the right-hand field the month. Simply turn to set the date for the next filter cartridge exchange. If the day when you next have to change the filter cartridge is not displayed on the indicator simply turn to the next number.

e.g. today is September 23rd, i.e. the filter cartridge is due to be changed on November 23rd. But because the number 23 is not shown on the exchange indicator set the exchange date to the 24th.