The annual calendar is one of the brand's most popular among Patek's plethora of replica watch complications. However, it may come as a shock to some that the annual calendar complication is relatively young, at a little over two decades old. Patek Philippe released the world's first annual calendar in 1996 with the ref. 5035 and followed it up with the ref. 5146 in 2005. Now, we will further talk about the details of the two versions. Calendar watches come in many forms. For example, there are the simple date watches and the slightly more complicated, day and date watches. Then there are complex calendar watches that can indicate day, date, month, and moon phase. What's more, there are also perpetual calendars and annual calendar watches among them. A perpetual calendar watch adjusts to exactly indicate the date in perpetuity because the complication accounts for leap years too. However, the scheduled leap year is skipped, so even a perpetual calendar will need manual adjusting - but none of us will be alive then, so that is not what we are concerning! However, an annual calendar needs a hands-on correction once a year. An annual calendar can differentiate between months with 30 days and 31 days, but not for February, which has either 28 days or 29 days. Therefore, when February turns into March, the wearer has to manually adjust the calendar to continue on the correct course every year. The dials of the Annual Calendar 5035 pack a lot of information. There is a luminescent leaf-shaped hand at the center which sweeps around the dial, pointing to the luminescent Roman numerals. As with most modern replica Patek Philippe watches, the back is full of sapphire crystal for a clear view of the movement inside. In addition to design changes, the Annual Calendar ref. 5146 also gives even more displays on the dial. Along with the time, date, day, and month, the current Patek annual calendar model also has a moon phase display and a power reserve indicator. The lume-filled Roman numerals of the older model were replaced with a mix of Arabic and faceted indexes, accompanied by small lume plots on the outer railroad minute track. On the contrary, the platinum version only has faceted indices and has no numerals at all for its hour markers. No matter which version of the replica Patek Philippe Annual Calendar reference you choose for, these watches stand for a meaningful milestone in the brand's long and storied history. It is not often that we see completely new inventions in modern horology. These complicated fine timepieces by Patek illustrate obviously that you're never too old to make creations.