In a nutshell, the annual calendar displays the day, date and month and is capable of independently adjusting for months with 30 or 31 days, automatically updating to the correct date at the end of the month. https://www.replicawatches.to Unlike a perpetual calendar however, an annual calendar cannot automatically adjust for the 28 (or 29) days of February, which means it requires a single adjustment once a year, at the end of February, to switch to the 1st of March.