How old is your lens? Here is how to determine the age of Canon lens using date codes and serial numbers
Canon has been transitioning to a 10-digit lens serial number (starting in 2008) and ending the inclusion of a separate manufacturing date code. While date codes and the shorter serial number are still found on some lenses, this inclusion will likely end completely. We loved the date code because it made aging a lens easy. However, now we can age a lens based on the serial number alone. For information on determining the age of a pre-10-digit serial number lens, see the section on interpreting the old date code below.
These dates should be viewed as approximations and should be used for your amusement as the estimates are not guaranteed correct. Please send any discrepancies you find. Note that Canon EOS DSLR camera body serial numbers, at least for 2013, do not follow this chart. Also please note that future dates shown in the table are predictions/expectations. The third digit in the serial number C may be a charge/batch type of number. Canon has been using this number to indicate lenses needing specific service-related updates such as firmware.
To determine the age of a pre-10-digit serial number Canon lens bearing a date code:
Until phasing out the practice starting in 2008, Canon included a date code beside the rear lens element of many (but not all) lenses (note that some 2012-manufactured lenses retain the date code). This code is also present on some other Canon products including camera bodies. The date code (as seen below) is in the form of "UV0511". The first letter "U" indicates that the lens was made in Canon's Utsunomiya, Japan factory. Prior to 1986, this letter is moved to the last position of the date code.
The second letter "V" is a year code that indicates the year of manufacture. Canon increments this letter each year starting with A in 1986 and prior to that, A in 1960 without the leading factory code. Here is a list to make things simple:
A = 2012, 1986, 1960
The first two numbers "05" is the month number the lens was manufactured in. Month 05 is May.