In some datasheet (two example in links below) I see only this information, about production date, in marking code explanation:
Date code (A : 1997.1)
If there was a further value I could think per induction but only with this information I can't figure out how to interpret the letters.
My capacitor (Matsuo type 553) have the second row: 63VM. The "63V" means rating 63V but the M what date mean? Maybe it is one date among 1998.1, 2000.3, 2002.5, 2004.7, 2006.9, 2008.11, 2011.1, 2013.3 and so on?
Or there is another way to count?
This is what say the datasheet:
(from: NCC-Matsuo metallized pet film capacitor – My capacitor)
And there it's another example:
(from: Jaro Components Tantalum Cap)
Best Answer
The Matsuo date code is explained in more detail in their other datasheets, such as p. 2 of the Matsuo Tantalum Solid Electrolytic Capacitors datasheet.
The codes repeat every 4 years:
The 12 uppercase letters A through M (minus "I") represent the 12 months Jan through December for one of the years 1997, 2001, 2005, 2009, 2013, 2017, ...
The 12 uppercase letters N through Z (minus "O") represent the 12 months Jan through December for one of the years 1998, 2002, 2006, 2010, 2014, 2018, ...
The 12 lowercase letters a through m (minus "i") represent the 12 months Jan through December for one of the years 1999, 2003, 2007, 2011, 2015, 2019, ...
The 12 lowercase letters n through z (minus "o") represent the 12 months Jan through December for one of the years 2000, 2004, 2008, 2012, 2016, 2020, ...
The capacitor you have with date code "M" was apparently manufactured in December in one of the years 1997, 2001, 2005, 2009, or 2013. (Since you had it in your hands June 2016 we can rule out any later years).
The Jaro date code looks like it might be exactly the same as the Matsuo date code.